{"id":1413,"date":"2024-06-02T23:00:25","date_gmt":"2024-06-02T23:00:25","guid":{"rendered":""},"modified":"2024-06-05T06:12:46","modified_gmt":"2024-06-04T22:12:46","slug":"typescript-%e4%b9%8b-more-on-functions","status":"publish","type":"post","link":"https:\/\/www.lccc.top\/?p=1413","title":{"rendered":"TypeScript \u4e4b More on Functions"},"content":{"rendered":"\n

\u524d\u8a00<\/h2>\n

TypeScript \u7684\u5b98\u65b9\u6587\u6863\u65e9\u5df2\u66f4\u65b0\uff0c\u4f46\u6211\u80fd\u627e\u5230\u7684\u4e2d\u6587\u6587\u6863\u90fd\u8fd8\u505c\u7559\u5728\u6bd4\u8f83\u8001\u7684\u7248\u672c\u3002\u6240\u4ee5\u5bf9\u5176\u4e2d\u65b0\u589e\u4ee5\u53ca\u4fee\u8ba2\u8f83\u591a\u7684\u4e00\u4e9b\u7ae0\u8282\u8fdb\u884c\u4e86\u7ffb\u8bd1\u6574\u7406\u3002<\/p>\n

\u672c\u7bc7\u6574\u7406\u81ea TypeScript Handbook \u4e2d \u300cMore on Functions<\/a>\u300d \u7ae0\u8282\u3002<\/p>\n

\u672c\u6587\u5e76\u4e0d\u4e25\u683c\u6309\u7167\u539f\u6587\u7ffb\u8bd1\uff0c\u5bf9\u90e8\u5206\u5185\u5bb9\u4e5f\u505a\u4e86\u89e3\u91ca\u8865\u5145\u3002<\/p>\n

\u6b63\u6587<\/h2>\n

\u51fd\u6570\u662f\u4efb\u4f55\u5e94\u7528\u7684\u57fa\u7840\u7ec4\u6210\u90e8\u5206\uff0c\u65e0\u8bba\u5b83\u662f\u5c40\u90e8\u51fd\u6570\uff08local functions\uff09\uff0c\u8fd8\u662f\u4ece\u5176\u4ed6\u6a21\u5757\u5bfc\u5165\u7684\u51fd\u6570\uff0c\u4ea6\u6216\u662f\u7c7b\u4e2d\u7684\u65b9\u6cd5\u3002\u5f53\u7136\uff0c\u51fd\u6570\u4e5f\u662f\u503c (values)\uff0c\u800c\u4e14\u50cf\u5176\u4ed6\u503c\u4e00\u6837\uff0cTypeScript \u6709\u5f88\u591a\u79cd\u65b9\u5f0f\u7528\u6765\u63cf\u8ff0\uff0c\u51fd\u6570\u53ef\u4ee5\u4ee5\u600e\u6837\u7684\u65b9\u5f0f\u88ab\u8c03\u7528\u3002\u8ba9\u6211\u4eec\u6765\u5b66\u4e60\u4e00\u4e0b\u5982\u4f55\u4e66\u5199\u63cf\u8ff0\u51fd\u6570\u7684\u7c7b\u578b\uff08types\uff09\u3002<\/p>\n

\u51fd\u6570\u7c7b\u578b\u8868\u8fbe\u5f0f\uff08Function Type Expressions\uff09<\/h2>\n

\u6700\u7b80\u5355\u63cf\u8ff0\u4e00\u4e2a\u51fd\u6570\u7684\u65b9\u5f0f\u662f\u4f7f\u7528**\u51fd\u6570\u7c7b\u578b\u8868\u8fbe\u5f0f\uff08function type expression\uff09\u3002**\u5b83\u7684\u5199\u6cd5\u6709\u70b9\u7c7b\u4f3c\u4e8e\u7bad\u5934\u51fd\u6570\uff1a<\/p>\n

<\/p>\n
function<\/span> greeter<\/span>(<\/span>fn<\/span>: (<\/span>a<\/span>: string<\/span>)<\/span> =><\/span> void<\/span><\/span>)<\/span> {<\/span>\n  fn<\/span>(<\/span>\"Hello, World\"<\/span>)<\/span>;<\/span>\n}<\/span>\n \nfunction<\/span> printToConsole<\/span>(<\/span>s<\/span>: string<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>s<\/span>)<\/span>;<\/span>\n}<\/span>\n \ngreeter<\/span>(<\/span>printToConsole<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u8bed\u6cd5 (a: string) => void<\/code> \u8868\u793a\u4e00\u4e2a\u51fd\u6570\u6709\u4e00\u4e2a\u540d\u4e3a a<\/code> \uff0c\u7c7b\u578b\u662f\u5b57\u7b26\u4e32\u7684\u53c2\u6570\uff0c\u8fd9\u4e2a\u51fd\u6570\u5e76\u6ca1\u6709\u8fd4\u56de\u4efb\u4f55\u503c\u3002<\/p>\n
\u5982\u679c\u4e00\u4e2a\u51fd\u6570\u53c2\u6570\u7684\u7c7b\u578b\u5e76\u6ca1\u6709\u660e\u786e\u7ed9\u51fa\uff0c\u5b83\u4f1a\u88ab\u9690\u5f0f\u8bbe\u7f6e\u4e3a any<\/code>\u3002<\/p>\n
\n
\u6ce8\u610f\u51fd\u6570\u53c2\u6570\u7684\u540d\u5b57\u662f\u5fc5\u987b\u7684\uff0c\u8fd9\u79cd\u51fd\u6570\u7c7b\u578b\u63cf\u8ff0 (string) => void<\/code>\uff0c\u8868\u793a\u7684\u5176\u5b9e\u662f\u4e00\u4e2a\u51fd\u6570\u6709\u4e00\u4e2a\u7c7b\u578b\u662f any<\/code>\uff0c\u540d\u4e3a string<\/code> \u7684\u53c2\u6570\u3002<\/p>\n<\/blockquote>\n
\u5f53\u7136\u4e86\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u4f7f\u7528\u7c7b\u578b\u522b\u540d\uff08type alias\uff09\u5b9a\u4e49\u4e00\u4e2a\u51fd\u6570\u7c7b\u578b\uff1a<\/p>\n
<\/p>\n
type<\/span> GreetFunction<\/span> =<\/span> (<\/span>a<\/span>: string<\/span>)<\/span> =><\/span> void<\/span><\/span>;<\/span>\nfunction<\/span> greeter<\/span>(<\/span>fn<\/span>: GreetFunction<\/span>)<\/span> {<\/span>\n  \/\/ ...<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u8c03\u7528\u7b7e\u540d\uff08Call Signatures\uff09<\/h2>\n
\u5728 JavaScript \u4e2d\uff0c\u51fd\u6570\u9664\u4e86\u53ef\u4ee5\u88ab\u8c03\u7528\uff0c\u81ea\u5df1\u4e5f\u662f\u53ef\u4ee5\u6709\u5c5e\u6027\u503c\u7684\u3002\u7136\u800c\u4e0a\u4e00\u8282\u8bb2\u5230\u7684\u51fd\u6570\u7c7b\u578b\u8868\u8fbe\u5f0f\u5e76\u4e0d\u80fd\u652f\u6301\u58f0\u660e\u5c5e\u6027\uff0c\u5982\u679c\u6211\u4eec\u60f3\u63cf\u8ff0\u4e00\u4e2a\u5e26\u6709\u5c5e\u6027\u7684\u51fd\u6570\uff0c\u6211\u4eec\u53ef\u4ee5\u5728\u4e00\u4e2a\u5bf9\u8c61\u7c7b\u578b\u4e2d\u5199\u4e00\u4e2a\u8c03\u7528\u7b7e\u540d\uff08call signature\uff09\u3002<\/p>\n
<\/p>\n
type<\/span> DescribableFunction<\/span> =<\/span> {<\/span>\n  description<\/span>: string<\/span>;<\/span>\n  (<\/span>someArg<\/span>: number<\/span>)<\/span>: boolean<\/span>;<\/span>\n}<\/span>;<\/span>\nfunction<\/span> doSomething<\/span>(<\/span>fn<\/span>: DescribableFunction<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>fn<\/span>.<\/span>description<\/span> +<\/span> \" returned \"<\/span> +<\/span> fn<\/span>(<\/span>6<\/span>)<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u6ce8\u610f\u8fd9\u4e2a\u8bed\u6cd5\u8ddf\u51fd\u6570\u7c7b\u578b\u8868\u8fbe\u5f0f\u7a0d\u6709\u4e0d\u540c\uff0c\u5728\u53c2\u6570\u5217\u8868\u548c\u8fd4\u56de\u7684\u7c7b\u578b\u4e4b\u95f4\u7528\u7684\u662f :<\/code> \u800c\u4e0d\u662f =><\/code>\u3002<\/p>\n
\u6784\u9020\u7b7e\u540d \uff08Construct Signatures\uff09<\/h2>\n
JavaScript \u51fd\u6570\u4e5f\u53ef\u4ee5\u4f7f\u7528 new<\/code> \u64cd\u4f5c\u7b26\u8c03\u7528\uff0c\u5f53\u88ab\u8c03\u7528\u7684\u65f6\u5019\uff0cTypeScript \u4f1a\u8ba4\u4e3a\u8fd9\u662f\u4e00\u4e2a\u6784\u9020\u51fd\u6570(constructors)\uff0c\u56e0\u4e3a\u4ed6\u4eec\u4f1a\u4ea7\u751f\u4e00\u4e2a\u65b0\u5bf9\u8c61\u3002\u4f60\u53ef\u4ee5\u5199\u4e00\u4e2a\u6784\u9020\u7b7e\u540d\uff0c\u65b9\u6cd5\u662f\u5728\u8c03\u7528\u7b7e\u540d\u524d\u9762\u52a0\u4e00\u4e2a new<\/code> \u5173\u952e\u8bcd\uff1a<\/p>\n
<\/p>\n
type<\/span> SomeConstructor<\/span> =<\/span> {<\/span>\n  new<\/span> (<\/span>s<\/span>: string<\/span>)<\/span>: SomeObject<\/span>;<\/span>\n}<\/span>;<\/span>\nfunction<\/span> fn<\/span>(<\/span>ctor<\/span>: SomeConstructor<\/span>)<\/span> {<\/span>\n  return<\/span> new<\/span> ctor<\/span>(<\/span>\"hello\"<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u4e00\u4e9b\u5bf9\u8c61\uff0c\u6bd4\u5982 Date<\/code> \u5bf9\u8c61\uff0c\u53ef\u4ee5\u76f4\u63a5\u8c03\u7528\uff0c\u4e5f\u53ef\u4ee5\u4f7f\u7528 new<\/code> \u64cd\u4f5c\u7b26\u8c03\u7528\uff0c\u800c\u4f60\u53ef\u4ee5\u5c06\u8c03\u7528\u7b7e\u540d\u548c\u6784\u9020\u7b7e\u540d\u5408\u5e76\u5728\u4e00\u8d77\uff1a<\/p>\n
<\/p>\n
interface<\/span> CallOrConstruct<\/span> {<\/span>\n  new<\/span> (<\/span>s<\/span>: string<\/span>)<\/span>: Date<\/span>;<\/span>\n  (<\/span>n<\/span>?: number<\/span>)<\/span>: number<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u6cdb\u578b\u51fd\u6570 \uff08Generic Functions\uff09<\/h2>\n
\u6211\u4eec\u7ecf\u5e38\u9700\u8981\u5199\u8fd9\u79cd\u51fd\u6570\uff0c\u5373\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u4f9d\u8d56\u51fd\u6570\u7684\u8f93\u5165\u7c7b\u578b\uff0c\u6216\u8005\u4e24\u4e2a\u8f93\u5165\u7684\u7c7b\u578b\u4ee5\u67d0\u79cd\u5f62\u5f0f\u76f8\u4e92\u5173\u8054\u3002\u8ba9\u6211\u4eec\u8003\u8651\u8fd9\u6837\u4e00\u4e2a\u51fd\u6570\uff0c\u5b83\u8fd4\u56de\u6570\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7d20\uff1a<\/p>\n
<\/p>\n
function<\/span> firstElement<\/span>(<\/span>arr<\/span>: any<\/span>[<\/span>]<\/span>)<\/span> {<\/span>\n  return<\/span> arr<\/span>[<\/span>0<\/span>]<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u6ce8\u610f\u6b64\u65f6\u51fd\u6570\u8fd4\u56de\u503c\u7684\u7c7b\u578b\u662f any<\/code>\uff0c\u5982\u679c\u80fd\u8fd4\u56de\u7b2c\u4e00\u4e2a\u5143\u7d20\u7684\u5177\u4f53\u7c7b\u578b\u5c31\u66f4\u597d\u4e86\u3002<\/p>\n
\u5728 TypeScript \u4e2d\uff0c\u6cdb\u578b\u5c31\u662f\u88ab\u7528\u6765\u63cf\u8ff0\u4e24\u4e2a\u503c\u4e4b\u95f4\u7684\u5bf9\u5e94\u5173\u7cfb\u3002\u6211\u4eec\u9700\u8981\u5728\u51fd\u6570\u7b7e\u540d\u91cc\u58f0\u660e\u4e00\u4e2a\u7c7b\u578b\u53c2\u6570 (type parameter)<\/strong>\uff1a<\/p>\n
<\/p>\n
function<\/span> firstElement<\/span><<\/span>Type<\/span>><\/span>(<\/span>arr<\/span>: Type<\/span>[<\/span>]<\/span>)<\/span>: Type<\/span> |<\/span> undefined<\/span> {<\/span>\n  return<\/span> arr<\/span>[<\/span>0<\/span>]<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u901a\u8fc7\u7ed9\u51fd\u6570\u6dfb\u52a0\u4e00\u4e2a\u7c7b\u578b\u53c2\u6570 Type<\/code>\uff0c\u5e76\u4e14\u5728\u4e24\u4e2a\u5730\u65b9\u4f7f\u7528\u5b83\uff0c\u6211\u4eec\u5c31\u5728\u51fd\u6570\u7684\u8f93\u5165(\u5373\u6570\u7ec4)\u548c\u51fd\u6570\u7684\u8f93\u51fa(\u5373\u8fd4\u56de\u503c)\u4e4b\u95f4\u521b\u5efa\u4e86\u4e00\u4e2a\u5173\u8054\u3002\u73b0\u5728\u5f53\u6211\u4eec\u8c03\u7528\u5b83\uff0c\u4e00\u4e2a\u66f4\u5177\u4f53\u7684\u7c7b\u578b\u5c31\u4f1a\u88ab\u5224\u65ad\u51fa\u6765\uff1a<\/p>\n
<\/p>\n
\/\/ s is of type 'string'<\/span>\nconst<\/span> s<\/span> =<\/span> firstElement<\/span>(<\/span>[<\/span>\"a\"<\/span>,<\/span> \"b\"<\/span>,<\/span> \"c\"<\/span>]<\/span>)<\/span>;<\/span>\n\/\/ n is of type 'number'<\/span>\nconst<\/span> n<\/span> =<\/span> firstElement<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>)<\/span>;<\/span>\n\/\/ u is of type undefined<\/span>\nconst<\/span> u<\/span> =<\/span> firstElement<\/span>(<\/span>[<\/span>]<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u63a8\u65ad\uff08Inference\uff09<\/h3>\n
\u6ce8\u610f\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u6ca1\u6709\u660e\u786e\u6307\u5b9a Type<\/code> \u7684\u7c7b\u578b\uff0c\u7c7b\u578b\u662f\u88ab TypeScript \u81ea\u52a8\u63a8\u65ad\u51fa\u6765\u7684\u3002<\/p>\n
\u6211\u4eec\u4e5f\u53ef\u4ee5\u4f7f\u7528\u591a\u4e2a\u7c7b\u578b\u53c2\u6570\uff0c\u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n
<\/p>\n
function<\/span> map<\/span><<\/span>Input<\/span>,<\/span> Output<\/span>><\/span>(<\/span>arr<\/span>: Input<\/span>[<\/span>]<\/span>,<\/span> func<\/span>: (<\/span>arg<\/span>: Input<\/span>)<\/span> =><\/span> Output<\/span>)<\/span>: Output<\/span>[<\/span>]<\/span> {<\/span>\n  return<\/span> arr<\/span>.<\/span>map<\/span>(<\/span>func<\/span>)<\/span>;<\/span>\n}<\/span>\n \n\/\/ Parameter 'n' is of type 'string'<\/span>\n\/\/ 'parsed' is of type 'number[]'<\/span>\nconst<\/span> parsed<\/span> =<\/span> map<\/span>(<\/span>[<\/span>\"1\"<\/span>,<\/span> \"2\"<\/span>,<\/span> \"3\"<\/span>]<\/span>,<\/span> (<\/span>n<\/span>)<\/span> =><\/span> parseInt<\/span>(<\/span>n<\/span>)<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u6ce8\u610f\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0cTypeScript \u65e2\u53ef\u4ee5\u63a8\u65ad\u51fa Input \u7684\u7c7b\u578b \uff08\u4ece\u4f20\u5165\u7684 string<\/code> \u6570\u7ec4\uff09\uff0c\u53c8\u53ef\u4ee5\u6839\u636e\u51fd\u6570\u8868\u8fbe\u5f0f\u7684\u8fd4\u56de\u503c\u63a8\u65ad\u51fa Output<\/code> \u7684\u7c7b\u578b\u3002<\/p>\n
\u7ea6\u675f\uff08Constraints\uff09<\/h3>\n
\u6709\u7684\u65f6\u5019\uff0c\u6211\u4eec\u60f3\u5173\u8054\u4e24\u4e2a\u503c\uff0c\u4f46\u53ea\u80fd\u64cd\u4f5c\u503c\u7684\u4e00\u4e9b\u56fa\u5b9a\u5b57\u6bb5\uff0c\u8fd9\u79cd\u60c5\u51b5\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528**\u7ea6\u675f\uff08constraint\uff09**\u5bf9\u7c7b\u578b\u53c2\u6570\u8fdb\u884c\u9650\u5236\u3002<\/p>\n
\u8ba9\u6211\u4eec\u5199\u4e00\u4e2a\u51fd\u6570\uff0c\u51fd\u6570\u8fd4\u56de\u4e24\u4e2a\u503c\u4e2d\u66f4\u957f\u7684\u90a3\u4e2a\u3002\u4e3a\u6b64\uff0c\u6211\u4eec\u9700\u8981\u4fdd\u8bc1\u4f20\u5165\u7684\u503c\u6709\u4e00\u4e2a number<\/code> \u7c7b\u578b\u7684 length<\/code> \u5c5e\u6027\u3002\u6211\u4eec\u4f7f\u7528  extends<\/code>  \u8bed\u6cd5\u6765\u7ea6\u675f\u51fd\u6570\u53c2\u6570\uff1a<\/p>\n
<\/p>\n
function<\/span> longest<\/span><<\/span>Type<\/span> extends<\/span> {<\/span> length<\/span>: number<\/span> }<\/span>><\/span>(<\/span>a<\/span>: Type<\/span>,<\/span> b<\/span>: Type<\/span>)<\/span> {<\/span>\n  if<\/span> (<\/span>a<\/span>.<\/span>length<\/span> >=<\/span> b<\/span>.<\/span>length<\/span>)<\/span> {<\/span>\n    return<\/span> a<\/span>;<\/span>\n  }<\/span> else<\/span> {<\/span>\n    return<\/span> b<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n \n\/\/ longerArray is of type 'number[]'<\/span>\nconst<\/span> longerArray<\/span> =<\/span> longest<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>]<\/span>,<\/span> [<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>)<\/span>;<\/span>\n\/\/ longerString is of type 'alice' | 'bob'<\/span>\nconst<\/span> longerString<\/span> =<\/span> longest<\/span>(<\/span>\"alice\"<\/span>,<\/span> \"bob\"<\/span>)<\/span>;<\/span>\n\/\/ Error! Numbers don't have a 'length' property<\/span>\nconst<\/span> notOK<\/span> =<\/span> longest<\/span>(<\/span>10<\/span>,<\/span> 100<\/span>)<\/span>;<\/span>\n\/\/ Argument of type 'number' is not assignable to parameter of type '{ length: number; }'.<\/span><\/pre>\n<\/div>\n
TypeScript \u4f1a\u63a8\u65ad longest<\/code> \u7684\u8fd4\u56de\u7c7b\u578b\uff0c\u6240\u4ee5\u8fd4\u56de\u503c\u7684\u7c7b\u578b\u63a8\u65ad\u5728\u6cdb\u578b\u51fd\u6570\u91cc\u4e5f\u662f\u9002\u7528\u7684\u3002<\/p>\n
\u6b63\u662f\u56e0\u4e3a\u6211\u4eec\u5bf9 Type<\/code> \u505a\u4e86 { length: number }<\/code> \u9650\u5236\uff0c\u6211\u4eec\u624d\u53ef\u4ee5\u88ab\u5141\u8bb8\u83b7\u53d6 a<\/code> b<\/code>\u53c2\u6570\u7684 .length<\/code> \u5c5e\u6027\u3002\u6ca1\u6709\u8fd9\u4e2a\u7c7b\u578b\u7ea6\u675f\uff0c\u6211\u4eec\u751a\u81f3\u4e0d\u80fd\u83b7\u53d6\u8fd9\u4e9b\u5c5e\u6027\uff0c\u56e0\u4e3a\u8fd9\u4e9b\u503c\u4e5f\u8bb8\u662f\u5176\u4ed6\u7c7b\u578b\uff0c\u5e76\u6ca1\u6709 length \u5c5e\u6027\u3002<\/p>\n
\u57fa\u4e8e\u4f20\u5165\u7684\u53c2\u6570\uff0clongerArray<\/code>\u548c longerString<\/code> \u4e2d\u7684\u7c7b\u578b\u90fd\u88ab\u63a8\u65ad\u51fa\u6765\u4e86\u3002\u8bb0\u4f4f\uff0c\u6240\u8c13\u6cdb\u578b\u5c31\u662f\u7528\u4e00\u4e2a\u76f8\u540c\u7c7b\u578b\u6765\u5173\u8054\u4e24\u4e2a\u6216\u8005\u66f4\u591a\u7684\u503c\u3002<\/p>\n
\u6cdb\u578b\u7ea6\u675f\u5b9e\u6218\uff08Working with Constrained Values\uff09<\/h3>\n
\u8fd9\u662f\u4e00\u4e2a\u4f7f\u7528\u6cdb\u578b\u7ea6\u675f\u5e38\u51fa\u73b0\u7684\u9519\u8bef\uff1a<\/p>\n
<\/p>\n
function<\/span> minimumLength<\/span><<\/span>Type<\/span> extends<\/span> {<\/span> length<\/span>: number<\/span> }<\/span>><\/span>(<\/span>\n  obj<\/span>: Type<\/span>,<\/span>\n  minimum<\/span>: number<\/span>\n)<\/span>: Type<\/span> {<\/span>\n  if<\/span> (<\/span>obj<\/span>.<\/span>length<\/span> >=<\/span> minimum<\/span>)<\/span> {<\/span>\n    return<\/span> obj<\/span>;<\/span>\n  }<\/span> else<\/span> {<\/span>\n    return<\/span> {<\/span> length<\/span>: minimum<\/span> }<\/span>;<\/span>\n    \/\/ Type '{ length: number; }' is not assignable to type 'Type'.<\/span>\n    \/\/ '{ length: number; }' is assignable to the constraint of type 'Type', but 'Type' could be instantiated with a different subtype of constraint '{ length: number; }'.<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u8fd9\u4e2a\u51fd\u6570\u770b\u8d77\u6765\u50cf\u662f\u6ca1\u6709\u95ee\u9898\uff0cType<\/code> \u88ab { length: number}<\/code> \u7ea6\u675f\uff0c\u51fd\u6570\u8fd4\u56de Type<\/code> \u6216\u8005\u4e00\u4e2a\u7b26\u5408\u7ea6\u675f\u7684\u503c\u3002<\/p>\n
\u800c\u8fd9\u5176\u4e2d\u7684\u95ee\u9898\u5c31\u5728\u4e8e\u51fd\u6570\u7406\u5e94\u8fd4\u56de\u4e0e\u4f20\u5165\u53c2\u6570\u76f8\u540c\u7c7b\u578b\u7684\u5bf9\u8c61\uff0c\u800c\u4e0d\u4ec5\u4ec5\u662f\u7b26\u5408\u7ea6\u675f\u7684\u5bf9\u8c61\u3002\u6211\u4eec\u53ef\u4ee5\u5199\u51fa\u8fd9\u6837\u4e00\u6bb5\u53cd\u4f8b\uff1a<\/p>\n
<\/p>\n
\/\/ 'arr' gets value { length: 6 }<\/span>\nconst<\/span> arr<\/span> =<\/span> minimumLength<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> 6<\/span>)<\/span>;<\/span>\n\/\/ and crashes here because arrays have<\/span>\n\/\/ a 'slice' method, but not the returned object!<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>arr<\/span>.<\/span>slice<\/span>(<\/span>0<\/span>)<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u58f0\u660e\u7c7b\u578b\u53c2\u6570 \uff08Specifying Type Arguments\uff09<\/h3>\n
TypeScript \u901a\u5e38\u80fd\u81ea\u52a8\u63a8\u65ad\u6cdb\u578b\u8c03\u7528\u4e2d\u4f20\u5165\u7684\u7c7b\u578b\u53c2\u6570\uff0c\u4f46\u4e5f\u5e76\u4e0d\u80fd\u603b\u662f\u63a8\u65ad\u51fa\u3002\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u6709\u8fd9\u6837\u4e00\u4e2a\u5408\u5e76\u4e24\u4e2a\u6570\u7ec4\u7684\u51fd\u6570\uff1a<\/p>\n
<\/p>\n
function<\/span> combine<\/span><<\/span>Type<\/span>><\/span>(<\/span>arr1<\/span>: Type<\/span>[<\/span>]<\/span>,<\/span> arr2<\/span>: Type<\/span>[<\/span>]<\/span>)<\/span>: Type<\/span>[<\/span>]<\/span> {<\/span>\n  return<\/span> arr1<\/span>.<\/span>concat<\/span>(<\/span>arr2<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u5982\u679c\u4f60\u50cf\u4e0b\u9762\u8fd9\u6837\u8c03\u7528\u51fd\u6570\u5c31\u4f1a\u51fa\u73b0\u9519\u8bef\uff1a<\/p>\n
<\/p>\n
const<\/span> arr<\/span> =<\/span> combine<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> [<\/span>\"hello\"<\/span>]<\/span>)<\/span>;<\/span>\n\/\/ Type 'string' is not assignable to type 'number'.<\/span><\/pre>\n<\/div>\n
\u800c\u5982\u679c\u4f60\u6267\u610f\u8981\u8fd9\u6837\u505a\uff0c\u4f60\u53ef\u4ee5\u624b\u52a8\u6307\u5b9a Type<\/code>\uff1a<\/p>\n
\n
const<\/span> arr<\/span> =<\/span> combine<\/span><<\/span>string<\/span> |<\/span> number<\/span>><\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> [<\/span>\"hello\"<\/span>]<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u5199\u4e00\u4e2a\u597d\u7684\u6cdb\u578b\u51fd\u6570\u7684\u4e00\u4e9b\u5efa\u8bae<\/h3>\n
\u5c3d\u7ba1\u5199\u6cdb\u578b\u51fd\u6570\u5f88\u6709\u610f\u601d\uff0c\u4f46\u4e5f\u5bb9\u6613\u7ffb\u8f66\u3002\u5982\u679c\u4f60\u4f7f\u7528\u4e86\u592a\u591a\u7684\u7c7b\u578b\u53c2\u6570\uff0c\u6216\u8005\u4f7f\u7528\u4e86\u4e00\u4e9b\u5e76\u4e0d\u9700\u8981\u7684\u7ea6\u675f\uff0c\u90fd\u53ef\u80fd\u4f1a\u5bfc\u81f4\u4e0d\u6b63\u786e\u7684\u7c7b\u578b\u63a8\u65ad\u3002<\/p>\n
\u7c7b\u578b\u53c2\u6570\u4e0b\u79fb\uff08Push Type Parameters Down\uff09<\/h4>\n
\u4e0b\u9762\u8fd9\u4e24\u4e2a\u51fd\u6570\u7684\u5199\u6cd5\u5f88\u76f8\u4f3c\uff1a<\/p>\n
<\/p>\n
function<\/span> firstElement1<\/span><<\/span>Type<\/span>><\/span>(<\/span>arr<\/span>: Type<\/span>[<\/span>]<\/span>)<\/span> {<\/span>\n  return<\/span> arr<\/span>[<\/span>0<\/span>]<\/span>;<\/span>\n}<\/span>\n \nfunction<\/span> firstElement2<\/span><<\/span>Type<\/span> extends<\/span> any<\/span>[<\/span>]<\/span>><\/span>(<\/span>arr<\/span>: Type<\/span>)<\/span> {<\/span>\n  return<\/span> arr<\/span>[<\/span>0<\/span>]<\/span>;<\/span>\n}<\/span>\n \n\/\/ a: number (good)<\/span>\nconst<\/span> a<\/span> =<\/span> firstElement1<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>)<\/span>;<\/span>\n\/\/ b: any (bad)<\/span>\nconst<\/span> b<\/span> =<\/span> firstElement2<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u7b2c\u4e00\u773c\u770b\u4e0a\u53bb\uff0c\u4e24\u4e2a\u51fd\u6570\u53ef\u592a\u76f8\u4f3c\u4e86\uff0c\u4f46\u662f\u7b2c\u4e00\u4e2a\u51fd\u6570\u7684\u5199\u6cd5\u53ef\u6bd4\u7b2c\u4e8c\u4e2a\u51fd\u6570\u597d\u592a\u591a\u4e86\u3002\u7b2c\u4e00\u4e2a\u51fd\u6570\u53ef\u4ee5\u63a8\u65ad\u51fa\u8fd4\u56de\u7684\u7c7b\u578b\u662f number<\/code>\uff0c\u4f46\u7b2c\u4e8c\u4e2a\u51fd\u6570\u63a8\u65ad\u7684\u8fd4\u56de\u7c7b\u578b\u5374\u662f any<\/code>\uff0c\u56e0\u4e3a TypeScript \u4e0d\u5f97\u4e0d\u7528\u7ea6\u675f\u7684\u7c7b\u578b\u6765\u63a8\u65ad arr[0]<\/code> \u8868\u8fbe\u5f0f\uff0c\u800c\u4e0d\u662f\u7b49\u5230\u51fd\u6570\u8c03\u7528\u7684\u65f6\u5019\u518d\u53bb\u63a8\u65ad\u8fd9\u4e2a\u5143\u7d20\u3002<\/p>\n
\u5173\u4e8e\u672c\u8282\u539f\u6587\u4e2d\u7684 push down<\/code> \u542b\u4e49\uff0c\u5728\u300a\u91cd\u6784\u300b\u91cc\uff0c\u5c31\u6709\u4e00\u4e2a\u51fd\u6570\u4e0b\u79fb\uff08Push Down Method\uff09\u7684\u4f18\u5316\u65b9\u6cd5\uff0c\u6307\u5982\u679c\u8d85\u7c7b\u4e2d\u7684\u67d0\u4e2a\u51fd\u6570\u53ea\u4e0e\u4e00\u4e2a\u6216\u8005\u5c11\u6570\u51e0\u4e2a\u5b50\u7c7b\u6709\u5173\uff0c\u90a3\u4e48\u6700\u597d\u5c06\u5176\u4ece\u8d85\u7c7b\u4e2d\u632a\u8d70\uff0c\u653e\u5230\u771f\u6b63\u5173\u5fc3\u5b83\u7684\u5b50\u7c7b\u4e2d\u53bb\u3002\u5373\u53ea\u5728\u8d85\u7c7b\u4fdd\u7559\u5171\u7528\u7684\u884c\u4e3a\u3002\u8fd9\u79cd\u5c06\u8d85\u7c7b\u4e2d\u7684\u51fd\u6570\u672c\u4f53\u590d\u5236\u5230\u5177\u4f53\u9700\u8981\u7684\u5b50\u7c7b\u7684\u65b9\u6cd5\u5c31\u53ef\u4ee5\u79f0\u4e4b\u4e3a “push down”\uff0c\u4e0e\u672c\u8282\u4e2d\u7684\u53bb\u9664 extend any[]<\/code>\uff0c\u5c06\u5176\u5177\u4f53\u7684\u63a8\u65ad\u4ea4\u7ed9 Type<\/code> \u81ea\u8eab\u5c31\u7c7b\u4f3c\u4e8e push down<\/code>\u3002<\/p>\n
\n
Rule: \u5982\u679c\u53ef\u80fd\u7684\u8bdd\uff0c\u76f4\u63a5\u4f7f\u7528\u7c7b\u578b\u53c2\u6570\u800c\u4e0d\u662f\u7ea6\u675f\u5b83<\/p>\n<\/blockquote>\n
\u4f7f\u7528\u66f4\u5c11\u7684\u7c7b\u578b\u53c2\u6570 (Use Fewer Type Parameters)<\/h4>\n
\u8fd9\u662f\u53e6\u4e00\u5bf9\u770b\u8d77\u6765\u5f88\u76f8\u4f3c\u7684\u51fd\u6570\uff1a<\/p>\n
<\/p>\n
function<\/span> filter1<\/span><<\/span>Type<\/span>><\/span>(<\/span>arr<\/span>: Type<\/span>[<\/span>]<\/span>,<\/span> func<\/span>: (<\/span>arg<\/span>: Type<\/span>)<\/span> =><\/span> boolean<\/span>)<\/span>: Type<\/span>[<\/span>]<\/span> {<\/span>\n  return<\/span> arr<\/span>.<\/span>filter<\/span>(<\/span>func<\/span>)<\/span>;<\/span>\n}<\/span>\n \nfunction<\/span> filter2<\/span><<\/span>Type<\/span>,<\/span> Func<\/span> extends<\/span> (<\/span>arg<\/span>: Type<\/span>)<\/span> =><\/span> boolean<\/span>><\/span>(<\/span>\n  arr<\/span>: Type<\/span>[<\/span>]<\/span>,<\/span>\n  func<\/span>: Func<\/span>\n)<\/span>: Type<\/span>[<\/span>]<\/span> {<\/span>\n  return<\/span> arr<\/span>.<\/span>filter<\/span>(<\/span>func<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u6211\u4eec\u521b\u5efa\u4e86\u4e00\u4e2a\u5e76\u6ca1\u6709\u5173\u8054\u4e24\u4e2a\u503c\u7684\u7c7b\u578b\u53c2\u6570 Func<\/code>\uff0c\u8fd9\u662f\u4e00\u4e2a\u5371\u9669\u4fe1\u53f7\uff0c\u56e0\u4e3a\u5b83\u610f\u5473\u7740\u8c03\u7528\u8005\u4e0d\u5f97\u4e0d\u6beb\u65e0\u7406\u7531\u7684\u624b\u52a8\u6307\u5b9a\u4e00\u4e2a\u989d\u5916\u7684\u7c7b\u578b\u53c2\u6570\u3002Func<\/code> \u4ec0\u4e48\u4e5f\u6ca1\u505a\uff0c\u5374\u5bfc\u81f4\u51fd\u6570\u66f4\u96be\u9605\u8bfb\u548c\u63a8\u65ad\u3002<\/p>\n
\n
Rule: \u5c3d\u53ef\u80fd\u7528\u66f4\u5c11\u7684\u7c7b\u578b\u53c2\u6570<\/p>\n<\/blockquote>\n
\u7c7b\u578b\u53c2\u6570\u5e94\u8be5\u51fa\u73b0\u4e24\u6b21 \uff08Type Parameters Should Appear Twice\uff09<\/h4>\n
\u6709\u7684\u65f6\u5019\u6211\u4eec\u4f1a\u5fd8\u8bb0\u4e00\u4e2a\u51fd\u6570\u5176\u5b9e\u5e76\u4e0d\u9700\u8981\u6cdb\u578b<\/p>\n
<\/p>\n
function<\/span> greet<\/span><<\/span>Str<\/span> extends<\/span> string<\/span>><\/span>(<\/span>s<\/span>: Str<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>\"Hello, \"<\/span> +<\/span> s<\/span>)<\/span>;<\/span>\n}<\/span>\n \ngreet<\/span>(<\/span>\"world\"<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u5176\u5b9e\u6211\u4eec\u53ef\u4ee5\u5982\u6b64\u7b80\u5355\u7684\u5199\u8fd9\u4e2a\u51fd\u6570\uff1a<\/p>\n
<\/p>\n
function<\/span> greet<\/span>(<\/span>s<\/span>: string<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>\"Hello, \"<\/span> +<\/span> s<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u8bb0\u4f4f\uff1a\u7c7b\u578b\u53c2\u6570\u662f\u7528\u6765\u5173\u8054\u591a\u4e2a\u503c\u4e4b\u95f4\u7684\u7c7b\u578b\u3002\u5982\u679c\u4e00\u4e2a\u7c7b\u578b\u53c2\u6570\u53ea\u5728\u51fd\u6570\u7b7e\u540d\u91cc\u51fa\u73b0\u4e86\u4e00\u6b21\uff0c\u90a3\u5b83\u5c31\u6ca1\u6709\u8ddf\u4efb\u4f55\u4e1c\u897f\u4ea7\u751f\u5173\u8054\u3002<\/p>\n
\n
Rule: \u5982\u679c\u4e00\u4e2a\u7c7b\u578b\u53c2\u6570\u4ec5\u4ec5\u51fa\u73b0\u5728\u4e00\u4e2a\u5730\u65b9\uff0c\u5f3a\u70c8\u5efa\u8bae\u4f60\u91cd\u65b0\u8003\u8651\u662f\u5426\u771f\u7684\u9700\u8981\u5b83<\/p>\n<\/blockquote>\n
\u53ef\u9009\u53c2\u6570\uff08Optional Parameters\uff09<\/h2>\n
JavaScript \u4e2d\u7684\u51fd\u6570\u7ecf\u5e38\u4f1a\u88ab\u4f20\u5165\u975e\u56fa\u5b9a\u6570\u91cf\u7684\u53c2\u6570\uff0c\u4e3e\u4e2a\u4f8b\u5b50\uff1anumber<\/code> \u7684 toFixed<\/code> \u65b9\u6cd5\u5c31\u652f\u6301\u4f20\u5165\u4e00\u4e2a\u53ef\u9009\u7684\u53c2\u6570\uff1a<\/p>\n
<\/p>\n
function<\/span> f<\/span>(<\/span>n<\/span>: number<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>n<\/span>.<\/span>toFixed<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 0 arguments<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>n<\/span>.<\/span>toFixed<\/span>(<\/span>3<\/span>)<\/span>)<\/span>;<\/span> \/\/ 1 argument<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 ?<\/code> \u8868\u793a\u8fd9\u4e2a\u53c2\u6570\u662f\u53ef\u9009\u7684\uff1a<\/p>\n
<\/p>\n
function<\/span> f<\/span>(<\/span>x<\/span>?: number<\/span>)<\/span> {<\/span>\n  \/\/ ...<\/span>\n}<\/span>\nf<\/span>(<\/span>)<\/span>;<\/span> \/\/ OK<\/span>\nf<\/span>(<\/span>10<\/span>)<\/span>;<\/span> \/\/ OK<\/span><\/pre>\n<\/div>\n
\u5c3d\u7ba1\u8fd9\u4e2a\u53c2\u6570\u88ab\u58f0\u660e\u4e3a number<\/code>\u7c7b\u578b\uff0cx<\/code> \u5b9e\u9645\u4e0a\u7684\u7c7b\u578b\u4e3a number | undefiend<\/code>\uff0c\u8fd9\u662f\u56e0\u4e3a\u5728 JavaScript \u4e2d\u672a\u6307\u5b9a\u7684\u51fd\u6570\u53c2\u6570\u5c31\u4f1a\u88ab\u8d4b\u503c undefined<\/code>\u3002<\/p>\n
\u4f60\u5f53\u7136\u4e5f\u53ef\u4ee5\u63d0\u4f9b\u6709\u4e00\u4e2a\u53c2\u6570\u9ed8\u8ba4\u503c\uff1a<\/p>\n
<\/p>\n
function<\/span> f<\/span>(<\/span>x<\/span> =<\/span> 10<\/span>)<\/span> {<\/span>\n  \/\/ ...<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u73b0\u5728\u5728 f<\/code> \u51fd\u6570\u4f53\u5185\uff0cx<\/code> \u7684\u7c7b\u578b\u4e3a number<\/code>\uff0c\u56e0\u4e3a\u4efb\u4f55 undefined<\/code> \u53c2\u6570\u90fd\u4f1a\u88ab\u66ff\u6362\u4e3a 10<\/code>\u3002\u6ce8\u610f\u5f53\u4e00\u4e2a\u53c2\u6570\u662f\u53ef\u9009\u7684\uff0c\u8c03\u7528\u7684\u65f6\u5019\u8fd8\u662f\u53ef\u4ee5\u4f20\u5165 undefined<\/code>\uff1a<\/p>\n
<\/p>\n
declare<\/span> function<\/span> f<\/span>(<\/span>x<\/span>?: number<\/span>)<\/span>: void<\/span><\/span>;<\/span>\n\/\/ cut<\/span>\n\/\/ All OK<\/span>\nf<\/span>(<\/span>)<\/span>;<\/span>\nf<\/span>(<\/span>10<\/span>)<\/span>;<\/span>\nf<\/span>(<\/span>undefined<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u56de\u8c03\u4e2d\u7684\u53ef\u9009\u53c2\u6570\uff08Optional Parameters in Callbacks\uff09<\/h3>\n
\u5728\u4f60\u5b66\u4e60\u8fc7\u53ef\u9009\u53c2\u6570\u548c\u51fd\u6570\u7c7b\u578b\u8868\u8fbe\u5f0f\u540e\uff0c\u4f60\u5f88\u5bb9\u6613\u5728\u5305\u542b\u4e86\u56de\u8c03\u51fd\u6570\u7684\u51fd\u6570\u4e2d\uff0c\u72af\u4e0b\u9762\u8fd9\u79cd\u9519\u8bef\uff1a<\/p>\n
<\/p>\n
function<\/span> myForEach<\/span>(<\/span>arr<\/span>: any<\/span>[<\/span>]<\/span>,<\/span> callback<\/span>: (<\/span>arg<\/span>: any<\/span>,<\/span> index<\/span>?: number<\/span>)<\/span> =><\/span> void<\/span><\/span>)<\/span> {<\/span>\n  for<\/span> (<\/span>let<\/span> i<\/span> =<\/span> 0<\/span>;<\/span> i<\/span> <<\/span> arr<\/span>.<\/span>length<\/span>;<\/span> i<\/span>++<\/span>)<\/span> {<\/span>\n    callback<\/span>(<\/span>arr<\/span>[<\/span>i<\/span>]<\/span>,<\/span> i<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u5c06 index?<\/code>\u4f5c\u4e3a\u4e00\u4e2a\u53ef\u9009\u53c2\u6570\uff0c\u672c\u610f\u662f\u5e0c\u671b\u4e0b\u9762\u8fd9\u4e9b\u8c03\u7528\u662f\u5408\u6cd5\u7684\uff1a<\/p>\n
<\/p>\n
myForEach<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> (<\/span>a<\/span>)<\/span> =><\/span> console<\/span>.<\/span>log<\/span>(<\/span>a<\/span>)<\/span>)<\/span>;<\/span>\nmyForEach<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> (<\/span>a<\/span>,<\/span> i<\/span>)<\/span> =><\/span> console<\/span>.<\/span>log<\/span>(<\/span>a<\/span>,<\/span> i<\/span>)<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u4f46 TypeScript \u5e76\u4e0d\u4f1a\u8fd9\u6837\u8ba4\u4e3a\uff0cTypeScript \u8ba4\u4e3a\u60f3\u8868\u8fbe\u7684\u662f\u56de\u8c03\u51fd\u6570\u53ef\u80fd\u53ea\u4f1a\u88ab\u4f20\u5165\u4e00\u4e2a\u53c2\u6570\uff0c\u6362\u53e5\u8bdd\u8bf4\uff0cmyForEach<\/code> \u51fd\u6570\u4e5f\u53ef\u80fd\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n
<\/p>\n
function<\/span> myForEach<\/span>(<\/span>arr<\/span>: any<\/span>[<\/span>]<\/span>,<\/span> callback<\/span>: (<\/span>arg<\/span>: any<\/span>,<\/span> index<\/span>?: number<\/span>)<\/span> =><\/span> void<\/span><\/span>)<\/span> {<\/span>\n  for<\/span> (<\/span>let<\/span> i<\/span> =<\/span> 0<\/span>;<\/span> i<\/span> <<\/span> arr<\/span>.<\/span>length<\/span>;<\/span> i<\/span>++<\/span>)<\/span> {<\/span>\n    \/\/ I don't feel like providing the index today<\/span>\n    callback<\/span>(<\/span>arr<\/span>[<\/span>i<\/span>]<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
TypeScript \u4f1a\u6309\u7167\u8fd9\u4e2a\u610f\u601d\u7406\u89e3\u5e76\u62a5\u9519\uff0c\u5c3d\u7ba1\u5b9e\u9645\u4e0a\u8fd9\u4e2a\u9519\u8bef\u5e76\u65e0\u53ef\u80fd\uff1a<\/p>\n
<\/p>\n
myForEach<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> (<\/span>a<\/span>,<\/span> i<\/span>)<\/span> =><\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>i<\/span>.<\/span>toFixed<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\n  \/\/ Object is possibly 'undefined'.<\/span>\n}<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u90a3\u5982\u4f55\u4fee\u6539\u5462\uff1f\u4e0d\u8bbe\u7f6e\u4e3a\u53ef\u9009\u53c2\u6570\u5176\u5b9e\u5c31\u53ef\u4ee5\uff1a<\/p>\n
<\/p>\n
function<\/span> myForEach<\/span>(<\/span>arr<\/span>: any<\/span>[<\/span>]<\/span>,<\/span> callback<\/span>: (<\/span>arg<\/span>: any<\/span>,<\/span> index<\/span>: number<\/span>)<\/span> =><\/span> void<\/span><\/span>)<\/span> {<\/span>\n  for<\/span> (<\/span>let<\/span> i<\/span> =<\/span> 0<\/span>;<\/span> i<\/span> <<\/span> arr<\/span>.<\/span>length<\/span>;<\/span> i<\/span>++<\/span>)<\/span> {<\/span>\n    callback<\/span>(<\/span>arr<\/span>[<\/span>i<\/span>]<\/span>,<\/span> i<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\nmyForEach<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> (<\/span>a<\/span>,<\/span> i<\/span>)<\/span> =><\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>a<\/span>)<\/span>;<\/span>\n}<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u5728 JavaScript \u4e2d\uff0c\u5982\u679c\u4f60\u8c03\u7528\u4e00\u4e2a\u51fd\u6570\u7684\u65f6\u5019\uff0c\u4f20\u5165\u4e86\u6bd4\u9700\u8981\u66f4\u591a\u7684\u53c2\u6570\uff0c\u989d\u5916\u7684\u53c2\u6570\u5c31\u4f1a\u88ab\u5ffd\u7565\u3002TypeScript \u4e5f\u662f\u540c\u6837\u7684\u505a\u6cd5\u3002<\/p>\n
\n
\u5f53\u4f60\u5199\u4e00\u4e2a\u56de\u8c03\u51fd\u6570\u7684\u7c7b\u578b\u65f6,\u4e0d\u8981\u5199\u4e00\u4e2a\u53ef\u9009\u53c2\u6570, \u9664\u975e\u4f60\u771f\u7684\u6253\u7b97\u8c03\u7528\u51fd\u6570\u7684\u65f6\u5019\u4e0d\u4f20\u5165\u5b9e\u53c2<\/p>\n<\/blockquote>\n
\u51fd\u6570\u91cd\u8f7d\uff08Function Overloads\uff09<\/h2>\n
\u4e00\u4e9b JavaScript \u51fd\u6570\u5728\u8c03\u7528\u7684\u65f6\u5019\u53ef\u4ee5\u4f20\u5165\u4e0d\u540c\u6570\u91cf\u548c\u7c7b\u578b\u7684\u53c2\u6570\u3002\u4e3e\u4e2a\u4f8b\u5b50\u3002\u4f60\u53ef\u4ee5\u5199\u4e00\u4e2a\u51fd\u6570\uff0c\u8fd4\u56de\u4e00\u4e2a\u65e5\u671f\u7c7b\u578b Date<\/code>\uff0c\u8fd9\u4e2a\u51fd\u6570\u63a5\u6536\u4e00\u4e2a\u65f6\u95f4\u6233\uff08\u4e00\u4e2a\u53c2\u6570\uff09\u6216\u8005\u4e00\u4e2a \u6708\/\u65e5\/\u5e74 \u7684\u683c\u5f0f (\u4e09\u4e2a\u53c2\u6570)\u3002<\/p>\n
\u5728 TypeScript \u4e2d\uff0c\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u5199\u91cd\u8f7d\u7b7e\u540d (overlaod signatures) \u8bf4\u660e\u4e00\u4e2a\u51fd\u6570\u7684\u4e0d\u540c\u8c03\u7528\u65b9\u6cd5\u3002 \u6211\u4eec\u9700\u8981\u5199\u4e00\u4e9b\u51fd\u6570\u7b7e\u540d (\u901a\u5e38\u4e24\u4e2a\u6216\u8005\u66f4\u591a)\uff0c\u7136\u540e\u518d\u5199\u51fd\u6570\u4f53\u7684\u5185\u5bb9\uff1a<\/p>\n
<\/p>\n
function<\/span> makeDate<\/span>(<\/span>timestamp<\/span>: number<\/span>)<\/span>: Date<\/span>;<\/span>\nfunction<\/span> makeDate<\/span>(<\/span>m<\/span>: number<\/span>,<\/span> d<\/span>: number<\/span>,<\/span> y<\/span>: number<\/span>)<\/span>: Date<\/span>;<\/span>\nfunction<\/span> makeDate<\/span>(<\/span>mOrTimestamp<\/span>: number<\/span>,<\/span> d<\/span>?: number<\/span>,<\/span> y<\/span>?: number<\/span>)<\/span>: Date<\/span> {<\/span>\n  if<\/span> (<\/span>d<\/span> !==<\/span> undefined<\/span> &&<\/span> y<\/span> !==<\/span> undefined<\/span>)<\/span> {<\/span>\n    return<\/span> new<\/span> Date<\/span>(<\/span>y<\/span>,<\/span> mOrTimestamp<\/span>,<\/span> d<\/span>)<\/span>;<\/span>\n  }<\/span> else<\/span> {<\/span>\n    return<\/span> new<\/span> Date<\/span>(<\/span>mOrTimestamp<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span>\nconst<\/span> d1<\/span> =<\/span> makeDate<\/span>(<\/span>12345678<\/span>)<\/span>;<\/span>\nconst<\/span> d2<\/span> =<\/span> makeDate<\/span>(<\/span>5<\/span>,<\/span> 5<\/span>,<\/span> 5<\/span>)<\/span>;<\/span>\nconst<\/span> d3<\/span> =<\/span> makeDate<\/span>(<\/span>1<\/span>,<\/span> 3<\/span>)<\/span>;<\/span>\n\n\/\/ No overload expects 2 arguments, but overloads do exist that expect either 1 or 3 arguments.<\/span><\/pre>\n<\/div>\n
\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u5199\u4e86\u4e24\u4e2a\u51fd\u6570\u91cd\u8f7d\uff0c\u4e00\u4e2a\u63a5\u53d7\u4e00\u4e2a\u53c2\u6570\uff0c\u53e6\u5916\u4e00\u4e2a\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u3002\u524d\u9762\u4e24\u4e2a\u51fd\u6570\u7b7e\u540d\u88ab\u79f0\u4e3a\u91cd\u8f7d\u7b7e\u540d (overload signatures)\u3002<\/p>\n
\u7136\u540e\uff0c\u6211\u4eec\u5199\u4e86\u4e00\u4e2a\u517c\u5bb9\u7b7e\u540d\u7684\u51fd\u6570\u5b9e\u73b0\uff0c\u6211\u4eec\u79f0\u4e4b\u4e3a\u5b9e\u73b0\u7b7e\u540d (implementation signature) \uff0c\u4f46\u8fd9\u4e2a\u7b7e\u540d\u4e0d\u80fd\u88ab\u76f4\u63a5\u8c03\u7528\u3002\u5c3d\u7ba1\u6211\u4eec\u5728\u51fd\u6570\u58f0\u660e\u4e2d\uff0c\u5728\u4e00\u4e2a\u5fc5\u987b\u53c2\u6570\u540e\uff0c\u58f0\u660e\u4e86\u4e24\u4e2a\u53ef\u9009\u53c2\u6570\uff0c\u5b83\u4f9d\u7136\u4e0d\u80fd\u88ab\u4f20\u5165\u4e24\u4e2a\u53c2\u6570\u8fdb\u884c\u8c03\u7528\u3002<\/p>\n
\u91cd\u8f7d\u7b7e\u540d\u548c\u5b9e\u73b0\u7b7e\u540d\uff08Overload Signatures and the Implementation Signature\uff09<\/h3>\n
\u8fd9\u662f\u4e00\u4e2a\u5e38\u89c1\u7684\u56f0\u60d1\u3002\u5927\u5bb6\u5e38\u4f1a\u8fd9\u6837\u5199\u4ee3\u7801\uff0c\u4f46\u662f\u53c8\u4e0d\u7406\u89e3\u4e3a\u4ec0\u4e48\u4f1a\u62a5\u9519\uff1a<\/p>\n
<\/p>\n
function<\/span> fn<\/span>(<\/span>x<\/span>: string<\/span>)<\/span>: void<\/span><\/span>;<\/span>\nfunction<\/span> fn<\/span>(<\/span>)<\/span> {<\/span>\n  \/\/ ...<\/span>\n}<\/span>\n\/\/ Expected to be able to call with zero arguments<\/span>\nfn<\/span>(<\/span>)<\/span>;<\/span>\nExpected<\/span> 1<\/span> arguments<\/span>,<\/span> but<\/span> got<\/span> 0.<\/span><\/pre>\n<\/div>\n
\u518d\u6b21\u5f3a\u8c03\u4e00\u4e0b\uff0c\u5199\u8fdb\u51fd\u6570\u4f53\u7684\u7b7e\u540d\u662f\u5bf9\u5916\u90e8\u6765\u8bf4\u662f\u201c\u4e0d\u53ef\u89c1\u201d\u7684\uff0c\u8fd9\u4e5f\u5c31\u610f\u5473\u7740\u5916\u754c\u201c\u770b\u4e0d\u5230\u201d\u5b83\u7684\u7b7e\u540d\uff0c\u81ea\u7136\u4e0d\u80fd\u6309\u7167\u5b9e\u73b0\u7b7e\u540d\u7684\u65b9\u5f0f\u6765\u8c03\u7528\u3002<\/p>\n
\n
\u5b9e\u73b0\u7b7e\u540d\u5bf9\u5916\u754c\u6765\u8bf4\u662f\u4e0d\u53ef\u89c1\u7684\u3002\u5f53\u5199\u4e00\u4e2a\u91cd\u8f7d\u51fd\u6570\u7684\u65f6\u5019\uff0c\u4f60\u5e94\u8be5\u603b\u662f\u9700\u8981\u6765\u4e24\u4e2a\u6216\u8005\u66f4\u591a\u7684\u7b7e\u540d\u5728\u5b9e\u73b0\u7b7e\u540d\u4e4b\u4e0a\u3002<\/p>\n<\/blockquote>\n
\u800c\u4e14\u5b9e\u73b0\u7b7e\u540d\u5fc5\u987b\u548c\u91cd\u8f7d\u7b7e\u540d\u5fc5\u987b\u517c\u5bb9\uff08compatible\uff09\uff0c\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u8fd9\u4e9b\u51fd\u6570\u4e4b\u6240\u4ee5\u62a5\u9519\u5c31\u662f\u56e0\u4e3a\u5b83\u4eec\u7684\u5b9e\u73b0\u7b7e\u540d\u5e76\u6ca1\u6709\u6b63\u786e\u7684\u548c\u91cd\u8f7d\u7b7e\u540d\u5339\u914d\u3002<\/p>\n
<\/p>\n
function<\/span> fn<\/span>(<\/span>x<\/span>: boolean<\/span>)<\/span>: void<\/span><\/span>;<\/span>\n\/\/ Argument type isn't right<\/span>\nfunction<\/span> fn<\/span>(<\/span>x<\/span>: string<\/span>)<\/span>: void<\/span><\/span>;<\/span>\n\/\/ This overload signature is not compatible with its implementation signature.<\/span>\nfunction<\/span> fn<\/span>(<\/span>x<\/span>: boolean<\/span>)<\/span> {<\/span>}<\/span><\/pre>\n<\/div>\n
<\/p>\n
function<\/span> fn<\/span>(<\/span>x<\/span>: string<\/span>)<\/span>: string<\/span>;<\/span>\n\/\/ Return type isn't right<\/span>\nfunction<\/span> fn<\/span>(<\/span>x<\/span>: number<\/span>)<\/span>: boolean<\/span>;<\/span>\nThis<\/span> overload<\/span> signature<\/span> is<\/span> not<\/span> compatible<\/span> with<\/span> its<\/span> implementation<\/span> signature<\/span>.<\/span>\nfunction<\/span> fn<\/span>(<\/span>x<\/span>: string<\/span> |<\/span> number<\/span>)<\/span> {<\/span>\n  return<\/span> \"oops\"<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u5199\u4e00\u4e2a\u597d\u7684\u51fd\u6570\u91cd\u8f7d\u7684\u4e00\u4e9b\u5efa\u8bae<\/h3>\n
\u5c31\u50cf\u6cdb\u578b\u4e00\u6837\uff0c\u4e5f\u6709\u4e00\u4e9b\u5efa\u8bae\u63d0\u4f9b\u7ed9\u4f60\u3002\u9075\u5faa\u8fd9\u4e9b\u539f\u5219\uff0c\u53ef\u4ee5\u8ba9\u4f60\u7684\u51fd\u6570\u66f4\u65b9\u4fbf\u8c03\u7528\u3001\u7406\u89e3\u3002<\/p>\n
\u8ba9\u6211\u4eec\u8bbe\u60f3\u8fd9\u6837\u4e00\u4e2a\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u8fd4\u56de\u6570\u7ec4\u6216\u8005\u5b57\u7b26\u4e32\u7684\u957f\u5ea6\uff1a<\/p>\n
<\/p>\n
function<\/span> len<\/span>(<\/span>s<\/span>: string<\/span>)<\/span>: number<\/span>;<\/span>\nfunction<\/span> len<\/span>(<\/span>arr<\/span>: any<\/span>[<\/span>]<\/span>)<\/span>: number<\/span>;<\/span>\nfunction<\/span> len<\/span>(<\/span>x<\/span>: any<\/span>)<\/span> {<\/span>\n  return<\/span> x<\/span>.<\/span>length<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u8fd9\u4e2a\u51fd\u6570\u4ee3\u7801\u529f\u80fd\u5b9e\u73b0\u4e86\uff0c\u4e5f\u6ca1\u6709\u4ec0\u4e48\u62a5\u9519\uff0c\u4f46\u6211\u4eec\u4e0d\u80fd\u4f20\u5165\u4e00\u4e2a\u53ef\u80fd\u662f\u5b57\u7b26\u4e32\u6216\u8005\u662f\u6570\u7ec4\u7684\u503c\uff0c\u56e0\u4e3a TypeScript \u53ea\u80fd\u4e00\u6b21\u7528\u4e00\u4e2a\u51fd\u6570\u91cd\u8f7d\u5904\u7406\u4e00\u6b21\u51fd\u6570\u8c03\u7528\u3002<\/p>\n
<\/p>\n
len<\/span>(<\/span>\"\"<\/span>)<\/span>;<\/span> \/\/ OK<\/span>\nlen<\/span>(<\/span>[<\/span>0<\/span>]<\/span>)<\/span>;<\/span> \/\/ OK<\/span>\nlen<\/span>(<\/span>Math<\/span>.<\/span>random<\/span>(<\/span>)<\/span> ><\/span> 0.5<\/span> ? \"hello\"<\/span> : [<\/span>0<\/span>]<\/span>)<\/span>;<\/span>\nNo<\/span> overload<\/span> matches<\/span> this<\/span> call<\/span>.<\/span>\n  Overload<\/span> 1<\/span> of<\/span> 2<\/span>,<\/span> '(s: string): number'<\/span>,<\/span> gave<\/span> the<\/span> following<\/span> error<\/span>.<\/span>\n    Argument<\/span> of<\/span> type<\/span> 'number[] | \"hello\"'<\/span> is<\/span> not<\/span> assignable<\/span> to<\/span> parameter<\/span> of<\/span> type<\/span> 'string'<\/span>.<\/span>\n      Type<\/span> 'number[]'<\/span> is<\/span> not<\/span> assignable<\/span> to<\/span> type<\/span> 'string'<\/span>.<\/span>\n  Overload<\/span> 2<\/span> of<\/span> 2<\/span>,<\/span> '(arr: any[]): number'<\/span>,<\/span> gave<\/span> the<\/span> following<\/span> error<\/span>.<\/span>\n    Argument<\/span> of<\/span> type<\/span> 'number[] | \"hello\"'<\/span> is<\/span> not<\/span> assignable<\/span> to<\/span> parameter<\/span> of<\/span> type<\/span> 'any[]'<\/span>.<\/span>\n      Type<\/span> 'string'<\/span> is<\/span> not<\/span> assignable<\/span> to<\/span> type<\/span> 'any[]'<\/span>.<\/span><\/pre>\n<\/div>\n
\u56e0\u4e3a\u4e24\u4e2a\u51fd\u6570\u91cd\u8f7d\u90fd\u6709\u76f8\u540c\u7684\u53c2\u6570\u6570\u91cf\u548c\u76f8\u540c\u7684\u8fd4\u56de\u7c7b\u578b\uff0c\u6211\u4eec\u53ef\u4ee5\u5199\u4e00\u4e2a\u65e0\u91cd\u8f7d\u7248\u672c\u7684\u51fd\u6570\u66ff\u4ee3\uff1a<\/p>\n
<\/p>\n
function<\/span> len<\/span>(<\/span>x<\/span>: any<\/span>[<\/span>]<\/span> |<\/span> string<\/span>)<\/span> {<\/span>\n  return<\/span> x<\/span>.<\/span>length<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u8fd9\u6837\u51fd\u6570\u5c31\u53ef\u4ee5\u4f20\u5165\u4e24\u4e2a\u7c7b\u578b\u4e2d\u7684\u4efb\u610f\u4e00\u4e2a\u4e86\u3002<\/p>\n
\n
\u5c3d\u53ef\u80fd\u7684\u4f7f\u7528\u8054\u5408\u7c7b\u578b\u66ff\u4ee3\u91cd\u8f7d<\/p>\n<\/blockquote>\n
\u5728\u51fd\u6570\u4e2d\u58f0\u660e this (Declaring this<\/code> in a Function)<\/h3>\n
TypeScript \u4f1a\u901a\u8fc7\u4ee3\u7801\u6d41\u5206\u6790\u51fd\u6570\u4e2d\u7684 this<\/code> \u4f1a\u662f\u4ec0\u4e48\u7c7b\u578b\uff0c\u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n
<\/p>\n
const<\/span> user<\/span> =<\/span> {<\/span>\n  id<\/span>: 123<\/span>,<\/span>\n \n  admin<\/span>: false<\/span>,<\/span>\n  becomeAdmin<\/span>: function<\/span> (<\/span>)<\/span> {<\/span>\n    this<\/span>.<\/span>admin<\/span> =<\/span> true<\/span>;<\/span>\n  }<\/span>,<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
TypeScript \u80fd\u591f\u7406\u89e3\u51fd\u6570 user.becomeAdmin<\/code> \u4e2d\u7684 this<\/code> \u6307\u5411\u7684\u662f\u5916\u5c42\u7684\u5bf9\u8c61 user<\/code>\uff0c\u8fd9\u5df2\u7ecf\u53ef\u4ee5\u5e94\u4ed8\u5f88\u591a\u60c5\u51b5\u4e86\uff0c\u4f46\u8fd8\u662f\u6709\u4e00\u4e9b\u60c5\u51b5\u9700\u8981\u4f60\u660e\u786e\u7684\u544a\u8bc9 TypeScript this<\/code> \u5230\u5e95\u4ee3\u8868\u7684\u662f\u4ec0\u4e48\u3002<\/p>\n
\u5728 JavaScript  \u4e2d\uff0cthis<\/code> \u662f\u4fdd\u7559\u5b57\uff0c\u6240\u4ee5\u4e0d\u80fd\u5f53\u505a\u53c2\u6570\u4f7f\u7528\u3002\u4f46 TypeScript \u53ef\u4ee5\u5141\u8bb8\u4f60\u5728\u51fd\u6570\u4f53\u5185\u58f0\u660e this<\/code> \u7684\u7c7b\u578b\u3002<\/p>\n
<\/p>\n
interface<\/span> DB<\/span> {<\/span>\n  filterUsers<\/span>(<\/span>filter<\/span>: (<\/span>this<\/span>: User<\/span>)<\/span> =><\/span> boolean<\/span>)<\/span>: User<\/span>[<\/span>]<\/span>;<\/span>\n}<\/span>\n \nconst<\/span> db<\/span> =<\/span> getDB<\/span>(<\/span>)<\/span>;<\/span>\nconst<\/span> admins<\/span> =<\/span> db<\/span>.<\/span>filterUsers<\/span>(<\/span>function<\/span> (<\/span>this<\/span>: User<\/span>)<\/span> {<\/span>\n  return<\/span> this<\/span>.<\/span>admin<\/span>;<\/span>\n}<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u8fd9\u4e2a\u5199\u6cd5\u6709\u70b9\u7c7b\u4f3c\u4e8e\u56de\u8c03\u98ce\u683c\u7684 API\u3002\u6ce8\u610f\u4f60\u9700\u8981\u4f7f\u7528 function<\/code> \u7684\u5f62\u5f0f\u800c\u4e0d\u80fd\u4f7f\u7528\u7bad\u5934\u51fd\u6570\uff1a<\/p>\n
<\/p>\n
interface<\/span> DB<\/span> {<\/span>\n  filterUsers<\/span>(<\/span>filter<\/span>: (<\/span>this<\/span>: User<\/span>)<\/span> =><\/span> boolean<\/span>)<\/span>: User<\/span>[<\/span>]<\/span>;<\/span>\n}<\/span>\n \nconst<\/span> db<\/span> =<\/span> getDB<\/span>(<\/span>)<\/span>;<\/span>\nconst<\/span> admins<\/span> =<\/span> db<\/span>.<\/span>filterUsers<\/span>(<\/span>(<\/span>)<\/span> =><\/span> this<\/span>.<\/span>admin<\/span>)<\/span>;<\/span>\n\/\/ The containing arrow function captures the global value of 'this'.<\/span>\n\/\/ Element implicitly has an 'any' type because type 'typeof globalThis' has no index signature.<\/span><\/pre>\n<\/div>\n
\u5176\u4ed6\u9700\u8981\u77e5\u9053\u7684\u7c7b\u578b\uff08Other Types to Know About\uff09<\/h2>\n
\u8fd9\u91cc\u4ecb\u7ecd\u4e00\u4e9b\u4e5f\u4f1a\u7ecf\u5e38\u51fa\u73b0\u7684\u7c7b\u578b\u3002\u50cf\u5176\u4ed6\u7684\u7c7b\u578b\u4e00\u6837\uff0c\u4f60\u4e5f\u53ef\u4ee5\u5728\u4efb\u4f55\u5730\u65b9\u4f7f\u7528\u5b83\u4eec\uff0c\u4f46\u5b83\u4eec\u7ecf\u5e38\u4e0e\u51fd\u6570\u642d\u914d\u4f7f\u7528\u3002<\/p>\n
void<\/code><\/h3>\n
void<\/code> \u8868\u793a\u4e00\u4e2a\u51fd\u6570\u5e76\u4e0d\u4f1a\u8fd4\u56de\u4efb\u4f55\u503c\uff0c\u5f53\u51fd\u6570\u5e76\u6ca1\u6709\u4efb\u4f55\u8fd4\u56de\u503c\uff0c\u6216\u8005\u8fd4\u56de\u4e0d\u4e86\u660e\u786e\u7684\u503c\u7684\u65f6\u5019\uff0c\u5c31\u5e94\u8be5\u7528\u8fd9\u79cd\u7c7b\u578b\u3002<\/p>\n
<\/p>\n
\/\/ The inferred return type is void<\/span>\nfunction<\/span> noop<\/span>(<\/span>)<\/span> {<\/span>\n  return<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u5728 JavaScript \u4e2d\uff0c\u4e00\u4e2a\u51fd\u6570\u5e76\u4e0d\u4f1a\u8fd4\u56de\u4efb\u4f55\u503c\uff0c\u4f1a\u9690\u5f0f\u8fd4\u56de undefined<\/code>\uff0c\u4f46\u662f void<\/code> \u548c undefined<\/code> \u5728 TypeScript \u4e2d\u5e76\u4e0d\u4e00\u6837\u3002\u5728\u672c\u6587\u7684\u6700\u540e\u4f1a\u6709\u66f4\u8be6\u7ec6\u7684\u4ecb\u7ecd\u3002<\/p>\n
\n
void  \u8ddf undefined \u4e0d\u4e00\u6837<\/p>\n<\/blockquote>\n
object<\/code><\/h3>\n
\u8fd9\u4e2a\u7279\u6b8a\u7684\u7c7b\u578b  object<\/code> \u53ef\u4ee5\u8868\u793a\u4efb\u4f55\u4e0d\u662f\u539f\u59cb\u7c7b\u578b\uff08primitive\uff09\u7684\u503c (string<\/code>\u3001number<\/code>\u3001bigint<\/code>\u3001boolean<\/code>\u3001symbol<\/code>\u3001null<\/code>\u3001undefined<\/code>)\u3002object<\/code> \u4e0d\u540c\u4e8e\u7a7a\u5bf9\u8c61\u7c7b\u578b { }<\/code>\uff0c\u4e5f\u4e0d\u540c\u4e8e\u5168\u5c40\u7c7b\u578b Object<\/code>\u3002\u5f88\u6709\u53ef\u80fd\u4f60\u4e5f\u7528\u4e0d\u5230 Object<\/code>\u3002<\/p>\n
\n
object \u4e0d\u540c\u4e8e Object<\/code> \uff0c\u603b\u662f\u7528 object<\/code>!<\/p>\n<\/blockquote>\n
\u6ce8\u610f\u5728 JavaScript \u4e2d\uff0c\u51fd\u6570\u5c31\u662f\u5bf9\u8c61\uff0c\u4ed6\u4eec\u53ef\u4ee5\u6709\u5c5e\u6027\uff0c\u5728\u4ed6\u4eec\u7684\u539f\u578b\u94fe\u4e0a\u6709 Object.prototype<\/code>\uff0c\u5e76\u4e14 instanceof Object<\/code>\u3002\u4f60\u53ef\u4ee5\u5bf9\u51fd\u6570\u4f7f\u7528 Object.keys<\/code> \u7b49\u7b49\u3002\u7531\u4e8e\u8fd9\u4e9b\u539f\u56e0\uff0c\u5728 TypeScript \u4e2d\uff0c\u51fd\u6570\u4e5f\u88ab\u8ba4\u4e3a\u662f object<\/code>\u3002<\/p>\n
unknown<\/code><\/h3>\n
unknown<\/code> \u7c7b\u578b\u53ef\u4ee5\u8868\u793a\u4efb\u4f55\u503c\u3002\u6709\u70b9\u7c7b\u4f3c\u4e8e any<\/code>\uff0c\u4f46\u662f\u66f4\u5b89\u5168\uff0c\u56e0\u4e3a\u5bf9 unknown<\/code> \u7c7b\u578b\u7684\u503c\u505a\u4efb\u4f55\u4e8b\u60c5\u90fd\u662f\u4e0d\u5408\u6cd5\u7684\uff1a<\/p>\n
<\/p>\n
function<\/span> f1<\/span>(<\/span>a<\/span>: any<\/span>)<\/span> {<\/span>\n  a<\/span>.<\/span>b<\/span>(<\/span>)<\/span>;<\/span> \/\/ OK<\/span>\n}<\/span>\nfunction<\/span> f2<\/span>(<\/span>a<\/span>: unknown<\/span>)<\/span> {<\/span>\n  a<\/span>.<\/span>b<\/span>(<\/span>)<\/span>;<\/span>\n  \/\/ Object is of type 'unknown'.<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u6709\u7684\u65f6\u5019\u7528\u6765\u63cf\u8ff0\u51fd\u6570\u7c7b\u578b\uff0c\u8fd8\u662f\u86ee\u6709\u7528\u7684\u3002\u4f60\u53ef\u4ee5\u63cf\u8ff0\u4e00\u4e2a\u51fd\u6570\u53ef\u4ee5\u63a5\u53d7\u4f20\u5165\u4efb\u4f55\u503c\uff0c\u4f46\u662f\u5728\u51fd\u6570\u4f53\u5185\u53c8\u4e0d\u7528\u5230 any<\/code> \u7c7b\u578b\u7684\u503c\u3002<\/p>\n
\u4f60\u53ef\u4ee5\u63cf\u8ff0\u4e00\u4e2a\u51fd\u6570\u8fd4\u56de\u4e00\u4e2a\u4e0d\u77e5\u9053\u4ec0\u4e48\u7c7b\u578b\u7684\u503c\uff0c\u6bd4\u5982\uff1a<\/p>\n
<\/p>\n
function<\/span> safeParse<\/span>(<\/span>s<\/span>: string<\/span>)<\/span>: unknown<\/span> {<\/span>\n  return<\/span> JSON<\/span>.<\/span>parse<\/span>(<\/span>s<\/span>)<\/span>;<\/span>\n}<\/span>\n \n\/\/ Need to be careful with 'obj'!<\/span>\nconst<\/span> obj<\/span> =<\/span> safeParse<\/span>(<\/span>someRandomString<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
never<\/code><\/h3>\n
\u4e00\u4e9b\u51fd\u6570\u4ece\u6765\u4e0d\u8fd4\u56de\u503c\uff1a<\/p>\n
<\/p>\n
function<\/span> fail<\/span>(<\/span>msg<\/span>: string<\/span>)<\/span>: never<\/span> {<\/span>\n  throw<\/span> new<\/span> Error<\/span>(<\/span>msg<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
never<\/code> \u7c7b\u578b\u8868\u793a\u4e00\u4e2a\u503c\u4e0d\u4f1a\u518d\u88ab\u89c2\u5bdf\u5230 (observed)\u3002<\/p>\n
\u4f5c\u4e3a\u4e00\u4e2a\u8fd4\u56de\u7c7b\u578b\u65f6\uff0c\u5b83\u8868\u793a\u8fd9\u4e2a\u51fd\u6570\u4f1a\u4e22\u4e00\u4e2a\u5f02\u5e38\uff0c\u6216\u8005\u4f1a\u7ed3\u675f\u7a0b\u5e8f\u7684\u6267\u884c\u3002<\/p>\n
\u5f53 TypeScript \u786e\u5b9a\u5728\u8054\u5408\u7c7b\u578b\u4e2d\u5df2\u7ecf\u6ca1\u6709\u53ef\u80fd\u662f\u5176\u4e2d\u7684\u7c7b\u578b\u7684\u65f6\u5019\uff0cnever<\/code> \u7c7b\u578b\u4e5f\u4f1a\u51fa\u73b0\uff1a<\/p>\n
<\/p>\n
function<\/span> fn<\/span>(<\/span>x<\/span>: string<\/span> |<\/span> number<\/span>)<\/span> {<\/span>\n  if<\/span> (<\/span>typeof<\/span> x<\/span> ===<\/span> \"string\"<\/span>)<\/span> {<\/span>\n    \/\/ do something<\/span>\n  }<\/span> else<\/span> if<\/span> (<\/span>typeof<\/span> x<\/span> ===<\/span> \"number\"<\/span>)<\/span> {<\/span>\n    \/\/ do something else<\/span>\n  }<\/span> else<\/span> {<\/span>\n    x<\/span>;<\/span> \/\/ has type 'never'!<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
Function<\/code><\/h3>\n
\u5728 JavaScript\uff0c\u5168\u5c40\u7c7b\u578b Function<\/code> \u63cf\u8ff0\u4e86 bind<\/code>\u3001call<\/code>\u3001apply<\/code> \u7b49\u5c5e\u6027\uff0c\u4ee5\u53ca\u5176\u4ed6\u6240\u6709\u7684\u51fd\u6570\u503c\u3002<\/p>\n
\u5b83\u4e5f\u6709\u4e00\u4e2a\u7279\u6b8a\u7684\u6027\u8d28\uff0c\u5c31\u662f Function<\/code> \u7c7b\u578b\u7684\u503c\u603b\u662f\u53ef\u4ee5\u88ab\u8c03\u7528\uff0c\u7ed3\u679c\u4f1a\u8fd4\u56de any<\/code> \u7c7b\u578b\uff1a<\/p>\n
<\/p>\n
function<\/span> doSomething<\/span>(<\/span>f<\/span>: Function<\/span>)<\/span> {<\/span>\n  f<\/span>(<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u8fd9\u662f\u4e00\u4e2a\u65e0\u7c7b\u578b\u51fd\u6570\u8c03\u7528 (untyped function call)\uff0c\u8fd9\u79cd\u8c03\u7528\u6700\u597d\u88ab\u907f\u514d\uff0c\u56e0\u4e3a\u5b83\u8fd4\u56de\u7684\u662f\u4e00\u4e2a\u4e0d\u5b89\u5168\u7684 any<\/code>\u7c7b\u578b\u3002<\/p>\n
\u5982\u679c\u4f60\u51c6\u5907\u63a5\u53d7\u4e00\u4e2a\u9ed1\u76d2\u7684\u51fd\u6570\uff0c\u4f46\u662f\u53c8\u4e0d\u6253\u7b97\u8c03\u7528\u5b83\uff0c() => void<\/code> \u4f1a\u66f4\u5b89\u5168\u4e00\u4e9b\u3002<\/p>\n
\u5269\u4f59\u53c2\u6570\uff08Rest Parameters and Arguments\uff09<\/h2>\n
parameters<\/code> \u4e0e arguments<\/code><\/h3>\n
arguments<\/code> \u548c parameters<\/code> \u90fd\u53ef\u4ee5\u8868\u793a\u51fd\u6570\u7684\u53c2\u6570\uff0c\u7531\u4e8e\u672c\u8282\u5185\u5bb9\u505a\u4e86\u5177\u4f53\u7684\u533a\u5206\uff0c\u6240\u4ee5\u6211\u4eec\u5b9a\u4e49 parameters<\/code> \u8868\u793a\u6211\u4eec\u5b9a\u4e49\u51fd\u6570\u65f6\u8bbe\u7f6e\u7684\u540d\u5b57\u5373\u5f62\u53c2\uff0carguments<\/code> \u8868\u793a\u6211\u4eec\u5b9e\u9645\u4f20\u5165\u51fd\u6570\u7684\u53c2\u6570\u5373\u5b9e\u53c2\u3002<\/p>\n
\u5269\u4f59\u53c2\u6570\uff08Rest Parameters\uff09<\/h3>\n
\u9664\u4e86\u7528\u53ef\u9009\u53c2\u6570\u3001\u91cd\u8f7d\u80fd\u8ba9\u51fd\u6570\u63a5\u6536\u4e0d\u540c\u6570\u91cf\u7684\u51fd\u6570\u53c2\u6570\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u901a\u8fc7\u4f7f\u7528\u5269\u4f59\u53c2\u6570\u8bed\u6cd5\uff08rest parameters\uff09\uff0c\u5b9a\u4e49\u4e00\u4e2a\u53ef\u4ee5\u4f20\u5165\u6570\u91cf\u4e0d\u53d7\u9650\u5236\u7684\u51fd\u6570\u53c2\u6570\u7684\u51fd\u6570\uff1a<\/p>\n
\u5269\u4f59\u53c2\u6570\u5fc5\u987b\u653e\u5728\u6240\u6709\u53c2\u6570\u7684\u6700\u540e\u9762\uff0c\u5e76\u4f7f\u7528 ...<\/code> \u8bed\u6cd5\uff1a<\/p>\n
<\/p>\n
function<\/span> multiply<\/span>(<\/span>n<\/span>: number<\/span>,<\/span> ...m<\/span>: number<\/span>[<\/span>]<\/span>)<\/span> {<\/span>\n  return<\/span> m<\/span>.<\/span>map<\/span>(<\/span>(<\/span>x<\/span>)<\/span> =><\/span> n<\/span> *<\/span> x<\/span>)<\/span>;<\/span>\n}<\/span>\n\/\/ 'a' gets value [10, 20, 30, 40]<\/span>\nconst<\/span> a<\/span> =<\/span> multiply<\/span>(<\/span>10<\/span>,<\/span> 1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> 4<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u5728 TypeScript \u4e2d\uff0c\u5269\u4f59\u53c2\u6570\u7684\u7c7b\u578b\u4f1a\u88ab\u9690\u5f0f\u8bbe\u7f6e\u4e3a any[]<\/code> \u800c\u4e0d\u662f any<\/code>\uff0c\u5982\u679c\u4f60\u8981\u8bbe\u7f6e\u5177\u4f53\u7684\u7c7b\u578b\uff0c\u5fc5\u987b\u662f Array<T><\/code> \u6216\u8005 T[]<\/code>\u7684\u5f62\u5f0f\uff0c\u518d\u6216\u8005\u5c31\u662f\u5143\u7ec4\u7c7b\u578b\uff08tuple type\uff09\u3002<\/p>\n
\u5269\u4f59\u53c2\u6570\uff08Rest Arguments\uff09<\/h3>\n
\u6211\u4eec\u53ef\u4ee5\u501f\u52a9\u4e00\u4e2a\u4f7f\u7528 ...<\/code> \u8bed\u6cd5\u7684\u6570\u7ec4\uff0c\u4e3a\u51fd\u6570\u63d0\u4f9b\u4e0d\u5b9a\u6570\u91cf\u7684\u5b9e\u53c2\u3002\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u6570\u7ec4\u7684 push<\/code> \u65b9\u6cd5\u5c31\u53ef\u4ee5\u63a5\u53d7\u4efb\u4f55\u6570\u91cf\u7684\u5b9e\u53c2\uff1a<\/p>\n
<\/p>\n
const<\/span> arr1<\/span> =<\/span> [<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>;<\/span>\nconst<\/span> arr2<\/span> =<\/span> [<\/span>4<\/span>,<\/span> 5<\/span>,<\/span> 6<\/span>]<\/span>;<\/span>\narr1<\/span>.<\/span>push<\/span>(<\/span>...arr2<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u6ce8\u610f\u4e00\u822c\u60c5\u51b5\u4e0b\uff0cTypeScript \u5e76\u4e0d\u4f1a\u5047\u5b9a\u6570\u7ec4\u662f\u4e0d\u53d8\u7684(immutable)\uff0c\u8fd9\u4f1a\u5bfc\u81f4\u4e00\u4e9b\u610f\u5916\u7684\u884c\u4e3a\uff1a<\/p>\n
<\/p>\n
\/\/ \u7c7b\u578b\u88ab\u63a8\u65ad\u4e3a number[] -- \"an array with zero or more numbers\",<\/span>\n\/\/ not specifically two numbers<\/span>\nconst<\/span> args<\/span> =<\/span> [<\/span>8<\/span>,<\/span> 5<\/span>]<\/span>;<\/span>\nconst<\/span> angle<\/span> =<\/span> Math<\/span>.<\/span>atan2<\/span>(<\/span>...args<\/span>)<\/span>;<\/span>\n\/\/ A spread argument must either have a tuple type or be passed to a rest parameter.<\/span><\/pre>\n<\/div>\n
\u4fee\u590d\u8fd9\u4e2a\u95ee\u9898\u9700\u8981\u4f60\u5199\u4e00\u70b9\u4ee3\u7801\uff0c\u901a\u5e38\u6765\u8bf4, \u4f7f\u7528 as const<\/code> \u662f\u6700\u76f4\u63a5\u6709\u6548\u7684\u89e3\u51b3\u65b9\u6cd5\uff1a<\/p>\n
<\/p>\n
\/\/ Inferred as 2-length tuple<\/span>\nconst<\/span> args<\/span> =<\/span> [<\/span>8<\/span>,<\/span> 5<\/span>]<\/span> as<\/span> const<\/span>;<\/span>\n\/\/ OK<\/span>\nconst<\/span> angle<\/span> =<\/span> Math<\/span>.<\/span>atan2<\/span>(<\/span>...args<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u901a\u8fc7 as const<\/code> \u8bed\u6cd5\u5c06\u5176\u53d8\u4e3a\u53ea\u8bfb\u5143\u7ec4\u4fbf\u53ef\u4ee5\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n
\u6ce8\u610f\u5f53\u4f60\u8981\u8fd0\u884c\u5728\u6bd4\u8f83\u8001\u7684\u73af\u5883\u65f6\uff0c\u4f7f\u7528\u5269\u4f59\u53c2\u6570\u8bed\u6cd5\u4e5f\u8bb8\u9700\u8981\u4f60\u5f00\u542f [downlevelIteration](https:\/\/www.typescriptlang.org\/tsconfig#downlevelIteration)<\/code> \uff0c\u5c06\u4ee3\u7801\u8f6c\u6362\u4e3a\u65e7\u7248\u672c\u7684 JavaScript\u3002<\/p>\n
\u53c2\u6570\u89e3\u6784\uff08Parameter Destructuring\uff09<\/h2>\n
\u4f60\u53ef\u4ee5\u4f7f\u7528\u53c2\u6570\u89e3\u6784\u65b9\u4fbf\u7684\u5c06\u4f5c\u4e3a\u53c2\u6570\u63d0\u4f9b\u7684\u5bf9\u8c61\u89e3\u6784\u4e3a\u51fd\u6570\u4f53\u5185\u4e00\u4e2a\u6216\u8005\u591a\u4e2a\u5c40\u90e8\u53d8\u91cf\uff0c\u5728 JavaScript \u4e2d\uff0c\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n
<\/p>\n
function<\/span> sum<\/span>(<\/span>{<\/span> a,<\/span> b,<\/span> c }<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>a<\/span> +<\/span> b<\/span> +<\/span> c<\/span>)<\/span>;<\/span>\n}<\/span>\nsum<\/span>(<\/span>{<\/span> a<\/span>: 10<\/span>,<\/span> b<\/span>: 3<\/span>,<\/span> c<\/span>: 9<\/span> }<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u5728\u89e3\u6784\u8bed\u6cd5\u540e\uff0c\u8981\u5199\u4e0a\u5bf9\u8c61\u7684\u7c7b\u578b\u6ce8\u89e3\uff1a<\/p>\n
<\/p>\n
function<\/span> sum<\/span>(<\/span>{<\/span> a,<\/span> b,<\/span> c }<\/span>: {<\/span> a<\/span>: number<\/span>;<\/span> b<\/span>: number<\/span>;<\/span> c<\/span>: number<\/span> }<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>a<\/span> +<\/span> b<\/span> +<\/span> c<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u8fd9\u4e2a\u770b\u8d77\u6765\u6709\u4e9b\u7e41\u7410\uff0c\u4f60\u4e5f\u53ef\u4ee5\u8fd9\u6837\u5199\uff1a<\/p>\n
<\/p>\n
\/\/ \u8ddf\u4e0a\u9762\u662f\u6709\u4e00\u6837\u7684<\/span>\ntype<\/span> ABC<\/span> =<\/span> {<\/span> a<\/span>: number<\/span>;<\/span> b<\/span>: number<\/span>;<\/span> c<\/span>: number<\/span> }<\/span>;<\/span>\nfunction<\/span> sum<\/span>(<\/span>{<\/span> a,<\/span> b,<\/span> c }<\/span>: ABC<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>a<\/span> +<\/span> b<\/span> +<\/span> c<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
\u51fd\u6570\u7684\u53ef\u8d4b\u503c\u6027 \uff08Assignability of Functions\uff09<\/h2>\n
\u8fd4\u56de void<\/code><\/h3>\n
\u51fd\u6570\u6709\u4e00\u4e2a void<\/code> \u8fd4\u56de\u7c7b\u578b\uff0c\u4f1a\u4ea7\u751f\u4e00\u4e9b\u610f\u6599\u4e4b\u5916\uff0c\u60c5\u7406\u4e4b\u4e2d\u7684\u884c\u4e3a\u3002<\/p>\n
\u5f53\u57fa\u4e8e\u4e0a\u4e0b\u6587\u7684\u7c7b\u578b\u63a8\u5bfc\uff08Contextual Typing\uff09\u63a8\u5bfc\u51fa\u8fd4\u56de\u7c7b\u578b\u4e3a void<\/code> \u7684\u65f6\u5019\uff0c\u5e76\u4e0d\u4f1a\u5f3a\u5236\u51fd\u6570\u4e00\u5b9a\u4e0d\u80fd\u8fd4\u56de\u5185\u5bb9\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u5982\u679c\u8fd9\u6837\u4e00\u4e2a\u8fd4\u56de void<\/code> \u7c7b\u578b\u7684\u51fd\u6570\u7c7b\u578b (type vf = () => void)<\/code>\uff0c
\n\u5f53\u88ab\u5e94\u7528\u7684\u65f6\u5019\uff0c\u4e5f\u662f\u53ef\u4ee5\u8fd4\u56de\u4efb\u4f55\u503c\u7684\uff0c\u4f46\u8fd4\u56de\u7684\u503c\u4f1a\u88ab\u5ffd\u7565\u6389\u3002<\/p>\n
\u56e0\u6b64\uff0c\u4e0b\u9762\u8fd9\u4e9b() => void<\/code> \u7c7b\u578b\u7684\u5b9e\u73b0\u90fd\u662f\u6709\u6548\u7684\uff1a<\/p>\n
<\/p>\n
type<\/span> voidFunc<\/span> =<\/span> (<\/span>)<\/span> =><\/span> void<\/span><\/span>;<\/span>\n \nconst<\/span> f1<\/span>: voidFunc<\/span> =<\/span> (<\/span>)<\/span> =><\/span> {<\/span>\n  return<\/span> true<\/span>;<\/span>\n}<\/span>;<\/span>\n \nconst<\/span> f2<\/span>: voidFunc<\/span> =<\/span> (<\/span>)<\/span> =><\/span> true<\/span>;<\/span>\n \nconst<\/span> f3<\/span>: voidFunc<\/span> =<\/span> function<\/span> (<\/span>)<\/span> {<\/span>\n  return<\/span> true<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
\u800c\u4e14\u5373\u4fbf\u8fd9\u4e9b\u51fd\u6570\u7684\u8fd4\u56de\u503c\u8d4b\u503c\u7ed9\u5176\u4ed6\u53d8\u91cf\uff0c\u4e5f\u4f1a\u7ef4\u6301 void<\/code> \u7c7b\u578b\uff1a<\/p>\n
<\/p>\n
const<\/span> v1<\/span> =<\/span> f1<\/span>(<\/span>)<\/span>;<\/span>\n \nconst<\/span> v2<\/span> =<\/span> f2<\/span>(<\/span>)<\/span>;<\/span>\n \nconst<\/span> v3<\/span> =<\/span> f3<\/span>(<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u6b63\u662f\u56e0\u4e3a\u8fd9\u4e2a\u7279\u6027\u7684\u5b58\u5728\uff0c\u6240\u4ee5\u63a5\u4e0b\u6765\u7684\u4ee3\u7801\u624d\u4f1a\u662f\u6709\u6548\u7684\uff1a<\/p>\n
<\/p>\n
const<\/span> src<\/span> =<\/span> [<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>;<\/span>\nconst<\/span> dst<\/span> =<\/span> [<\/span>0<\/span>]<\/span>;<\/span>\n \nsrc<\/span>.<\/span>forEach<\/span>(<\/span>(<\/span>el<\/span>)<\/span> =><\/span> dst<\/span>.<\/span>push<\/span>(<\/span>el<\/span>)<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u5c3d\u7ba1 Array.prototype.push<\/code> \u8fd4\u56de\u4e00\u4e2a\u6570\u5b57\uff0c\u5e76\u4e14 Array.prototype.forEach<\/code> \u65b9\u6cd5\u671f\u5f85\u4e00\u4e2a\u8fd4\u56de void<\/code> \u7c7b\u578b\u7684\u51fd\u6570\uff0c\u4f46\u8fd9\u6bb5\u4ee3\u7801\u4f9d\u7136\u6ca1\u6709\u62a5\u9519\u3002\u5c31\u662f\u56e0\u4e3a\u57fa\u4e8e\u4e0a\u4e0b\u6587\u63a8\u5bfc\uff0c\u63a8\u5bfc\u51fa forEach \u51fd\u6570\u8fd4\u56de\u7c7b\u578b\u4e3a void\uff0c\u6b63\u662f\u56e0\u4e3a\u4e0d\u5f3a\u5236\u51fd\u6570\u4e00\u5b9a\u4e0d\u80fd\u8fd4\u56de\u5185\u5bb9\uff0c\u6240\u4ee5\u4e0a\u9762\u8fd9\u79cd return dst.push(el)<\/code> \u7684\u5199\u6cd5\u624d\u4e0d\u4f1a\u62a5\u9519\u3002<\/p>\n
\u53e6\u5916\u8fd8\u6709\u4e00\u4e2a\u7279\u6b8a\u7684\u4f8b\u5b50\u9700\u8981\u6ce8\u610f\uff0c\u5f53\u4e00\u4e2a\u51fd\u6570\u5b57\u9762\u91cf\u5b9a\u4e49\u8fd4\u56de\u4e00\u4e2a void<\/code> \u7c7b\u578b\uff0c\u51fd\u6570\u662f\u4e00\u5b9a\u4e0d\u80fd\u8fd4\u56de\u4efb\u4f55\u4e1c\u897f\u7684\uff1a<\/p>\n
<\/p>\n
function<\/span> f2<\/span>(<\/span>)<\/span>: void<\/span><\/span> {<\/span>\n  \/\/ @ts-expect-error<\/span>\n  return<\/span> true<\/span>;<\/span>\n}<\/span>\n \nconst<\/span> f3<\/span> =<\/span> function<\/span> (<\/span>)<\/span>: void<\/span><\/span> {<\/span>\n  \/\/ @ts-expect-error<\/span>\n  return<\/span> true<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
TypeScript \u7cfb\u5217<\/h2>\n
TypeScript \u7cfb\u5217\u6587\u7ae0\u7531\u5b98\u65b9\u6587\u6863\u7ffb\u8bd1\u3001\u91cd\u96be\u70b9\u89e3\u6790\u3001\u5b9e\u6218\u6280\u5de7\u4e09\u4e2a\u90e8\u5206\u7ec4\u6210\uff0c\u6db5\u76d6\u5165\u95e8\u3001\u8fdb\u9636\u3001\u5b9e\u6218\uff0c\u65e8\u5728\u4e3a\u4f60\u63d0\u4f9b\u4e00\u4e2a\u7cfb\u7edf\u5b66\u4e60 TS \u7684\u6559\u7a0b\uff0c\u5168\u7cfb\u5217\u9884\u8ba1 40 \u7bc7\u5de6\u53f3\u3002\u70b9\u6b64\u6d4f\u89c8\u5168\u7cfb\u5217\u6587\u7ae0\uff0c\u5e76\u5efa\u8bae\u987a\u4fbf\u6536\u85cf\u7ad9\u70b9\u3002<\/a><\/p>\n
\u5fae\u4fe1\uff1a\u300cmqyqingfeng\u300d\uff0c\u52a0\u6211\u8fdb\u51b4\u7fbd\u552f\u4e00\u7684\u8bfb\u8005\u7fa4\u3002<\/p>\n<\/td>\n
\u6587\u7ae0\u8f6c\u8f7d\u81eahttps:\/\/github.com\/mqyqingfeng\/Blog\/issues\/220<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
\u524d\u8a00 TypeScript \u7684\u5b98\u65b9\u6587\u6863\u65e9\u5df2\u66f4\u65b0\uff0c\u4f46\u6211\u80fd\u627e\u5230\u7684\u4e2d\u6587\u6587\u6863\u90fd\u8fd8\u505c\u7559\u5728\u6bd4\u8f83\u8001\u7684\u7248\u672c\u3002\u6240\u4ee5\u5bf9\u5176\u4e2d\u65b0\u589e\u4ee5\u53ca\u4fee\u8ba2\u8f83\u591a\u7684\u4e00\u4e9b\u7ae0\u8282\u8fdb\u884c\u4e86\u7ffb\u8bd1\u6574\u7406\u3002 \u672c\u7bc7\u6574\u7406\u81ea T…<\/p>\n
 Read More  Read More<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1413","post","type-post","status-publish","format-standard","hentry","category-learn"],"_links":{"self":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1413"}],"collection":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1413"}],"version-history":[{"count":1,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1413\/revisions"}],"predecessor-version":[{"id":2401,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1413\/revisions\/2401"}],"wp:attachment":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1413"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1413"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1413"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}