{"id":1416,"date":"2024-06-02T23:02:07","date_gmt":"2024-06-02T23:02:07","guid":{"rendered":""},"modified":"2024-06-05T06:12:46","modified_gmt":"2024-06-04T22:12:46","slug":"typescript-%e4%b9%8b%e5%b8%b8%e8%a7%81%e7%b1%bb%e5%9e%8b%ef%bc%88%e4%b8%8a%ef%bc%89","status":"publish","type":"post","link":"https:\/\/www.lccc.top\/?p=1416","title":{"rendered":"TypeScript \u4e4b\u5e38\u89c1\u7c7b\u578b\uff08\u4e0a\uff09"},"content":{"rendered":"<td class=\"d-block comment-body markdown-body  js-comment-body\">\n<blockquote>\n<p dir=\"auto\">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<\/blockquote>\n<blockquote>\n<p dir=\"auto\">\u672c\u7bc7\u7ffb\u8bd1\u6574\u7406\u81ea TypeScript Handbook \u4e2d \u300c<a href=\"https:\/\/www.typescriptlang.org\/docs\/handbook\/2\/everyday-types.html\" rel=\"nofollow\">Everyday Types<\/a>\u300d \u7ae0\u8282\u3002<\/p>\n<\/blockquote>\n<blockquote>\n<p dir=\"auto\">\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<\/blockquote>\n<h2 dir=\"auto\">\u5e38\u89c1\u7c7b\u578b\uff08Everyday Types\uff09<\/h2>\n<p dir=\"auto\">\u672c\u7ae0\u6211\u4eec\u4f1a\u8bb2\u89e3 JavaScript \u4e2d\u6700\u5e38\u89c1\u7684\u4e00\u4e9b\u7c7b\u578b\uff0c\u4ee5\u53ca\u5bf9\u5e94\u7684\u63cf\u8ff0\u65b9\u5f0f\u3002\u6ce8\u610f\u672c\u7ae0\u5185\u5bb9\u5e76\u4e0d\u8be6\u5c3d\uff0c\u540e\u7eed\u7684\u7ae0\u8282\u4f1a\u8bb2\u89e3\u66f4\u591a\u547d\u540d\u548c\u4f7f\u7528\u7c7b\u578b\u7684\u65b9\u5f0f\u3002<\/p>\n<p dir=\"auto\">\u7c7b\u578b\u53ef\u4ee5\u51fa\u73b0\u5728\u5f88\u591a\u5730\u65b9\uff0c\u4e0d\u4ec5\u4ec5\u662f\u5728\u7c7b\u578b\u6ce8\u89e3 (type annotations)\u4e2d\u3002\u6211\u4eec\u4e0d\u4ec5\u8981\u5b66\u4e60\u7c7b\u578b\u672c\u8eab\uff0c\u4e5f\u8981\u5b66\u4e60\u5728\u4ec0\u4e48\u5730\u65b9\u4f7f\u7528\u8fd9\u4e9b\u7c7b\u578b\u4ea7\u751f\u65b0\u7684\u7ed3\u6784\u3002<\/p>\n<p dir=\"auto\">\u6211\u4eec\u5148\u590d\u4e60\u4e0b\u6700\u57fa\u672c\u548c\u5e38\u89c1\u7684\u7c7b\u578b\uff0c\u8fd9\u4e9b\u662f\u6784\u5efa\u66f4\u590d\u6742\u7c7b\u578b\u7684\u57fa\u7840\u3002<\/p>\n<h2 dir=\"auto\">\u539f\u59cb\u7c7b\u578b: <code class=\"notranslate\">string<\/code>\uff0c<code class=\"notranslate\">number<\/code> \u548c <code class=\"notranslate\">boolean<\/code>\uff08The primitives\uff09<\/h2>\n<p dir=\"auto\">JavaScript \u6709\u4e09\u4e2a\u975e\u5e38\u5e38\u7528\u7684<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Primitive\" rel=\"nofollow\">\u539f\u59cb\u7c7b\u578b<\/a>\uff1a<code class=\"notranslate\">string<\/code>\uff0c<code class=\"notranslate\">number<\/code> \u548c <code class=\"notranslate\">boolean<\/code>\uff0c\u6bcf\u4e00\u4e2a\u7c7b\u578b\u5728 TypeScript \u4e2d\u90fd\u6709\u5bf9\u5e94\u7684\u7c7b\u578b\u3002\u4ed6\u4eec\u7684\u540d\u5b57\u8ddf\u4f60\u5728 JavaScript \u4e2d\u4f7f\u7528 <code class=\"notranslate\">typeof<\/code> \u64cd\u4f5c\u7b26\u5f97\u5230\u7684\u7ed3\u679c\u662f\u4e00\u6837\u7684\u3002<\/p>\n<ul dir=\"auto\">\n<li><code class=\"notranslate\">string<\/code> \u8868\u793a\u5b57\u7b26\u4e32\uff0c\u6bd4\u5982 &#8220;Hello, world&#8221;<\/li>\n<li><code class=\"notranslate\">number<\/code> \u8868\u793a\u6570\u5b57\uff0c\u6bd4\u5982 <code class=\"notranslate\">42<\/code>\uff0cJavaScript \u4e2d\u6ca1\u6709 <code class=\"notranslate\">int<\/code> \u6216\u8005 <code class=\"notranslate\">float<\/code>\uff0c\u6240\u6709\u7684\u6570\u5b57\uff0c\u7c7b\u578b\u90fd\u662f <code class=\"notranslate\">number<\/code><\/li>\n<li><code class=\"notranslate\">boolean<\/code> \u8868\u793a\u5e03\u5c14\u503c\uff0c\u5176\u5b9e\u4e5f\u5c31\u4e24\u4e2a\u503c\uff1a <code class=\"notranslate\">true<\/code> \u548c <code class=\"notranslate\">false<\/code><br \/>\n\u200b<\/li>\n<\/ul>\n<blockquote>\n<p dir=\"auto\">\u7c7b\u578b\u540d <code class=\"notranslate\">String<\/code> \uff0c<code class=\"notranslate\">Number<\/code> \u548c <code class=\"notranslate\">Boolean<\/code> \uff08\u9996\u5b57\u6bcd\u5927\u5199\uff09\u4e5f\u662f\u5408\u6cd5\u7684\uff0c\u4f46\u5b83\u4eec\u662f\u4e00\u4e9b\u975e\u5e38\u5c11\u89c1\u7684\u7279\u6b8a\u5185\u7f6e\u7c7b\u578b\u3002\u6240\u4ee5\u7c7b\u578b\u603b\u662f\u4f7f\u7528 <code class=\"notranslate\">string<\/code> \uff0c<code class=\"notranslate\">number<\/code> \u6216\u8005 <code class=\"notranslate\">boolean<\/code> \u3002<\/p>\n<\/blockquote>\n<h2 dir=\"auto\">\u6570\u7ec4\uff08Array\uff09<\/h2>\n<p dir=\"auto\">\u58f0\u660e\u4e00\u4e2a\u7c7b\u4f3c\u4e8e <code class=\"notranslate\">[1, 2, 3]<\/code> \u7684\u6570\u7ec4\u7c7b\u578b\uff0c\u4f60\u9700\u8981\u7528\u5230\u8bed\u6cd5 <code class=\"notranslate\">number[]<\/code>\u3002\u8fd9\u4e2a\u8bed\u6cd5\u53ef\u4ee5\u9002\u7528\u4e8e\u4efb\u4f55\u7c7b\u578b\uff08\u4e3e\u4e2a\u4f8b\u5b50\uff0c<code class=\"notranslate\">string[]<\/code> \u8868\u793a\u4e00\u4e2a\u5b57\u7b26\u4e32\u6570\u7ec4\uff09\u3002\u4f60\u4e5f\u53ef\u80fd\u770b\u5230\u8fd9\u79cd\u5199\u6cd5 <code class=\"notranslate\">Array&lt;number&gt;<\/code>\uff0c\u662f\u4e00\u6837\u7684\u3002\u6211\u4eec\u4f1a\u5728\u6cdb\u578b\u7ae0\u8282\u4e3a\u5927\u5bb6\u4ecb\u7ecd <code class=\"notranslate\">T&lt;U&gt;<\/code> \u8bed\u6cd5\u3002<\/p>\n<blockquote>\n<p dir=\"auto\">\u6ce8\u610f <code class=\"notranslate\">[number]<\/code> \u548c <code class=\"notranslate\">number[]<\/code> \u8868\u793a\u4e0d\u540c\u7684\u610f\u601d\uff0c\u53c2\u8003<a href=\"https:\/\/www.typescriptlang.org\/docs\/handbook\/2\/objects.html#tuple-types\" rel=\"nofollow\">\u5143\u7ec4<\/a>\u7ae0\u8282<\/p>\n<\/blockquote>\n<h2 dir=\"auto\"><code class=\"notranslate\">any<\/code><\/h2>\n<p dir=\"auto\">TypeScript \u6709\u4e00\u4e2a\u7279\u6b8a\u7684\u7c7b\u578b\uff0c<code class=\"notranslate\">any<\/code>\uff0c\u5f53\u4f60\u4e0d\u5e0c\u671b\u4e00\u4e2a\u503c\u5bfc\u81f4\u7c7b\u578b\u68c0\u67e5\u9519\u8bef\u7684\u65f6\u5019\uff0c\u5c31\u53ef\u4ee5\u8bbe\u7f6e\u4e3a <code class=\"notranslate\">any<\/code> \u3002<\/p>\n<p dir=\"auto\">\u5f53\u4e00\u4e2a\u503c\u662f <code class=\"notranslate\">any<\/code> \u7c7b\u578b\u7684\u65f6\u5019\uff0c\u4f60\u53ef\u4ee5\u83b7\u53d6\u5b83\u7684\u4efb\u610f\u5c5e\u6027 (\u4e5f\u4f1a\u88ab\u8f6c\u4e3a <code class=\"notranslate\">any<\/code> \u7c7b\u578b)\uff0c\u6216\u8005\u50cf\u51fd\u6570\u4e00\u6837\u8c03\u7528\u5b83\uff0c\u628a\u5b83\u8d4b\u503c\u7ed9\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u503c\uff0c\u6216\u8005\u628a\u4efb\u610f\u7c7b\u578b\u7684\u503c\u8d4b\u503c\u7ed9\u5b83\uff0c\u518d\u6216\u8005\u662f\u5176\u4ed6\u8bed\u6cd5\u6b63\u786e\u7684\u64cd\u4f5c\uff0c\u90fd\u53ef\u4ee5\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content='let obj: any = { x: 0 };\n\/\/ None of the following lines of code will throw compiler errors.\n\/\/ Using `any` disables all further type checking, and it is assumed \n\/\/ you know the environment better than TypeScript.\nobj.foo();\nobj();\nobj.bar = 100;\nobj = \"hello\";\nconst n: number = obj;'><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">let<\/span> <span class=\"pl-s1\">obj<\/span>: <span class=\"pl-smi\">any<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">x<\/span>: <span class=\"pl-c1\">0<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-c\">\/\/ None of the following lines of code will throw compiler errors.<\/span>\n<span class=\"pl-c\">\/\/ Using `any` disables all further type checking, and it is assumed <\/span>\n<span class=\"pl-c\">\/\/ you know the environment better than TypeScript.<\/span>\n<span class=\"pl-s1\">obj<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">foo<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-en\">obj<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-s1\">obj<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">bar<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">100<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-s1\">obj<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-s\">\"hello\"<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-k\">const<\/span> <span class=\"pl-s1\">n<\/span>: <span class=\"pl-smi\">number<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-s1\">obj<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u5f53\u4f60\u4e0d\u60f3\u5199\u4e00\u4e2a\u957f\u957f\u7684\u7c7b\u578b\u4ee3\u7801\uff0c\u4ec5\u4ec5\u60f3\u8ba9 TypeScript \u77e5\u9053\u67d0\u6bb5\u7279\u5b9a\u7684\u4ee3\u7801\u662f\u6ca1\u6709\u95ee\u9898\u7684\uff0c<code class=\"notranslate\">any<\/code> \u7c7b\u578b\u662f\u5f88\u6709\u7528\u7684\u3002<\/p>\n<h3 dir=\"auto\"><code class=\"notranslate\">noImplicitAny<\/code><\/h3>\n<p dir=\"auto\">\u5982\u679c\u4f60\u6ca1\u6709\u6307\u5b9a\u4e00\u4e2a\u7c7b\u578b\uff0cTypeScript \u4e5f\u4e0d\u80fd\u4ece\u4e0a\u4e0b\u6587\u63a8\u65ad\u51fa\u5b83\u7684\u7c7b\u578b\uff0c\u7f16\u8bd1\u5668\u5c31\u4f1a\u9ed8\u8ba4\u8bbe\u7f6e\u4e3a <code class=\"notranslate\">any<\/code> \u7c7b\u578b\u3002<\/p>\n<p dir=\"auto\">\u5982\u679c\u4f60\u603b\u662f\u60f3\u907f\u514d\u8fd9\u79cd\u60c5\u51b5\uff0c\u6bd5\u7adf TypeScript \u5bf9 <code class=\"notranslate\">any<\/code> \u4e0d\u505a\u7c7b\u578b\u68c0\u67e5\uff0c\u4f60\u53ef\u4ee5\u5f00\u542f\u7f16\u8bd1\u9879 <a href=\"https:\/\/www.typescriptlang.org\/tsconfig#noImplicitAny\" rel=\"nofollow\">noImplicitAny<\/a>\uff0c\u5f53\u88ab\u9690\u5f0f\u63a8\u65ad\u4e3a <code class=\"notranslate\">any<\/code> \u65f6\uff0cTypeScript \u5c31\u4f1a\u62a5\u9519\u3002<\/p>\n<h2 dir=\"auto\">\u53d8\u91cf\u4e0a\u7684\u7c7b\u578b\u6ce8\u89e3\uff08Type Annotations on Variables\uff09<\/h2>\n<p dir=\"auto\">\u5f53\u4f60\u4f7f\u7528 <code class=\"notranslate\">const<\/code>\u3001<code class=\"notranslate\">var<\/code> \u6216 <code class=\"notranslate\">let<\/code> \u58f0\u660e\u4e00\u4e2a\u53d8\u91cf\u65f6\uff0c\u4f60\u53ef\u4ee5\u9009\u62e9\u6027\u7684\u6dfb\u52a0\u4e00\u4e2a\u7c7b\u578b\u6ce8\u89e3\uff0c\u663e\u5f0f\u6307\u5b9a\u53d8\u91cf\u7684\u7c7b\u578b\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content='let myName: string = \"Alice\";'>\n<pre class=\"notranslate\"><span class=\"pl-k\">let<\/span> <span class=\"pl-s1\">myName<\/span>: <span class=\"pl-smi\">string<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-s\">\"Alice\"<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<blockquote>\n<p dir=\"auto\">TypeScript \u5e76\u4e0d\u4f7f\u7528\u201c\u5728\u5de6\u8fb9\u8fdb\u884c\u7c7b\u578b\u58f0\u660e\u201d\u7684\u5f62\u5f0f\uff0c\u6bd4\u5982 <code class=\"notranslate\">int x = 0<\/code>\uff1b\u7c7b\u578b\u6ce8\u89e3\u5f80\u5f80\u8ddf\u5728\u8981\u88ab\u58f0\u660e\u7c7b\u578b\u7684\u5185\u5bb9\u540e\u9762\u3002<\/p>\n<\/blockquote>\n<p dir=\"auto\">\u4e0d\u8fc7\u5927\u90e8\u5206\u65f6\u5019\uff0c\u8fd9\u4e0d\u662f\u5fc5\u987b\u7684\u3002\u56e0\u4e3a TypeScript \u4f1a\u81ea\u52a8\u63a8\u65ad\u7c7b\u578b\u3002\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u53d8\u91cf\u7684\u7c7b\u578b\u53ef\u4ee5\u57fa\u4e8e\u521d\u59cb\u503c\u8fdb\u884c\u63a8\u65ad\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"\/\/ No type annotation needed -- 'myName' inferred as type 'string'\nlet myName = &quot;Alice&quot;;\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c\">\/\/ No type annotation needed -- 'myName' inferred as type 'string'<\/span>\n<span class=\"pl-k\">let<\/span> <span class=\"pl-s1\">myName<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-s\">\"Alice\"<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u5927\u90e8\u5206\u65f6\u5019\uff0c\u4f60\u4e0d\u9700\u8981\u5b66\u4e60\u63a8\u65ad\u7684\u89c4\u5219\u3002\u5982\u679c\u4f60\u521a\u5f00\u59cb\u4f7f\u7528\uff0c\u5c1d\u8bd5\u5c3d\u53ef\u80fd\u5c11\u7684\u4f7f\u7528\u7c7b\u578b\u6ce8\u89e3\u3002\u4f60\u4e5f\u8bb8\u4f1a\u60ca\u8bb6\u4e8e\uff0cTypeScript \u4ec5\u4ec5\u9700\u8981\u5f88\u5c11\u7684\u5185\u5bb9\u5c31\u53ef\u4ee5\u5b8c\u5168\u7406\u89e3\u5c06\u8981\u53d1\u751f\u7684\u4e8b\u60c5\u3002<\/p>\n<h2 dir=\"auto\">\u51fd\u6570\uff08Function\uff09<\/h2>\n<p dir=\"auto\">\u51fd\u6570\u662f JavaScript \u4f20\u9012\u6570\u636e\u7684\u4e3b\u8981\u65b9\u6cd5\u3002TypeScript \u5141\u8bb8\u4f60\u6307\u5b9a\u51fd\u6570\u7684\u8f93\u5165\u503c\u548c\u8f93\u51fa\u503c\u7684\u7c7b\u578b\u3002<\/p>\n<h3 dir=\"auto\">\u53c2\u6570\u7c7b\u578b\u6ce8\u89e3\uff08Parameter Type Annotations\uff09<\/h3>\n<p dir=\"auto\">\u5f53\u4f60\u58f0\u660e\u4e00\u4e2a\u51fd\u6570\u7684\u65f6\u5019\uff0c\u4f60\u53ef\u4ee5\u5728\u6bcf\u4e2a\u53c2\u6570\u540e\u9762\u6dfb\u52a0\u4e00\u4e2a\u7c7b\u578b\u6ce8\u89e3\uff0c\u58f0\u660e\u51fd\u6570\u53ef\u4ee5\u63a5\u53d7\u4ec0\u4e48\u7c7b\u578b\u7684\u53c2\u6570\u3002\u53c2\u6570\u7c7b\u578b\u6ce8\u89e3\u8ddf\u5728\u53c2\u6570\u540d\u5b57\u540e\u9762\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content='\/\/ Parameter type annotation\nfunction greet(name: string) {\n  console.log(\"Hello, \" + name.toUpperCase() + \"!!\");\n}'><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c\">\/\/ Parameter type annotation<\/span>\n<span class=\"pl-k\">function<\/span> <span class=\"pl-en\">greet<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">name<\/span>: <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"Hello, \"<\/span> <span class=\"pl-c1\">+<\/span> <span class=\"pl-s1\">name<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">toUpperCase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-c1\">+<\/span> <span class=\"pl-s\">\"!!\"<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u5f53\u53c2\u6570\u6709\u4e86\u7c7b\u578b\u6ce8\u89e3\u7684\u65f6\u5019\uff0cTypeScript \u4fbf\u4f1a\u68c0\u67e5\u51fd\u6570\u7684\u5b9e\u53c2\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"\/\/ Would be a runtime error if executed!\ngreet(42);\n\/\/ Argument of type 'number' is not assignable to parameter of type 'string'.\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c\">\/\/ Would be a runtime error if executed!<\/span>\n<span class=\"pl-en\">greet<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-c1\">42<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-c\">\/\/ Argument of type 'number' is not assignable to parameter of type 'string'.<\/span><\/pre>\n<\/div>\n<blockquote>\n<p dir=\"auto\">\u5373\u4fbf\u4f60\u5bf9\u53c2\u6570\u6ca1\u6709\u505a\u7c7b\u578b\u6ce8\u89e3\uff0cTypeScript \u4f9d\u7136\u4f1a\u68c0\u67e5\u4f20\u5165\u53c2\u6570\u7684\u6570\u91cf\u662f\u5426\u6b63\u786e<\/p>\n<\/blockquote>\n<h3 dir=\"auto\">\u8fd4\u56de\u503c\u7c7b\u578b\u6ce8\u89e3\uff08Return Type Annotations\uff09<\/h3>\n<p dir=\"auto\">\u4f60\u4e5f\u53ef\u4ee5\u6dfb\u52a0\u8fd4\u56de\u503c\u7684\u7c7b\u578b\u6ce8\u89e3\u3002\u8fd4\u56de\u503c\u7684\u7c7b\u578b\u6ce8\u89e3\u8ddf\u5728\u53c2\u6570\u5217\u8868\u540e\u9762\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function getFavoriteNumber(): number {\n  return 26;\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">getFavoriteNumber<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span>: <span class=\"pl-smi\">number<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-k\">return<\/span> <span class=\"pl-c1\">26<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u8ddf\u53d8\u91cf\u7c7b\u578b\u6ce8\u89e3\u4e00\u6837\uff0c\u4f60\u4e5f\u4e0d\u9700\u8981\u603b\u662f\u6dfb\u52a0\u8fd4\u56de\u503c\u7c7b\u578b\u6ce8\u89e3\uff0cTypeScript \u4f1a\u57fa\u4e8e\u5b83\u7684 <code class=\"notranslate\">return<\/code> \u8bed\u53e5\u63a8\u65ad\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\u3002\u50cf\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u7c7b\u578b\u6ce8\u89e3\u5199\u548c\u6ca1\u5199\u90fd\u662f\u4e00\u6837\u7684\uff0c\u4f46\u4e00\u4e9b\u4ee3\u7801\u5e93\u4f1a\u663e\u5f0f\u6307\u5b9a\u8fd4\u56de\u503c\u7684\u7c7b\u578b\uff0c\u53ef\u80fd\u662f\u56e0\u4e3a\u9700\u8981\u7f16\u5199\u6587\u6863\uff0c\u6216\u8005\u963b\u6b62\u610f\u5916\u4fee\u6539\uff0c\u4ea6\u6216\u8005\u4ec5\u4ec5\u662f\u4e2a\u4eba\u559c\u597d\u3002<\/p>\n<h3 dir=\"auto\">\u533f\u540d\u51fd\u6570\uff08Anonymous Functions\uff09<\/h3>\n<p dir=\"auto\">\u533f\u540d\u51fd\u6570\u6709\u4e00\u70b9\u4e0d\u540c\u4e8e\u51fd\u6570\u58f0\u660e\uff0c\u5f53 TypeScript \u77e5\u9053\u4e00\u4e2a\u533f\u540d\u51fd\u6570\u5c06\u88ab\u600e\u6837\u8c03\u7528\u7684\u65f6\u5019\uff0c\u533f\u540d\u51fd\u6570\u7684\u53c2\u6570\u4f1a\u88ab\u81ea\u52a8\u7684\u6307\u5b9a\u7c7b\u578b\u3002<\/p>\n<p dir=\"auto\">\u8fd9\u662f\u4e00\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"\/\/ No type annotations here, but TypeScript can spot the bug\nconst names = [&quot;Alice&quot;, &quot;Bob&quot;, &quot;Eve&quot;];\n \n\/\/ Contextual typing for function\nnames.forEach(function (s) {\n  console.log(s.toUppercase());\n  \/\/ Property 'toUppercase' does not exist on type 'string'. Did you mean 'toUpperCase'?\n});\n \n\/\/ Contextual typing also applies to arrow functions\nnames.forEach((s) =&gt; {\n  console.log(s.toUppercase());\n  \/\/ Property 'toUppercase' does not exist on type 'string'. Did you mean 'toUpperCase'?\n});\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c\">\/\/ No type annotations here, but TypeScript can spot the bug<\/span>\n<span class=\"pl-k\">const<\/span> <span class=\"pl-s1\">names<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-kos\">[<\/span><span class=\"pl-s\">\"Alice\"<\/span><span class=\"pl-kos\">,<\/span> <span class=\"pl-s\">\"Bob\"<\/span><span class=\"pl-kos\">,<\/span> <span class=\"pl-s\">\"Eve\"<\/span><span class=\"pl-kos\">]<\/span><span class=\"pl-kos\">;<\/span>\n \n<span class=\"pl-c\">\/\/ Contextual typing for function<\/span>\n<span class=\"pl-s1\">names<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">forEach<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-k\">function<\/span> <span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">s<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">s<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">toUppercase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-c\">\/\/ Property 'toUppercase' does not exist on type 'string'. Did you mean 'toUpperCase'?<\/span>\n<span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n \n<span class=\"pl-c\">\/\/ Contextual typing also applies to arrow functions<\/span>\n<span class=\"pl-s1\">names<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">forEach<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">s<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-c1\">=&gt;<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">s<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">toUppercase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-c\">\/\/ Property 'toUppercase' does not exist on type 'string'. Did you mean 'toUpperCase'?<\/span>\n<span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u5c3d\u7ba1\u53c2\u6570 <code class=\"notranslate\">s<\/code> \u5e76\u6ca1\u6709\u6dfb\u52a0\u7c7b\u578b\u6ce8\u89e3\uff0c\u4f46 TypeScript \u6839\u636e <code class=\"notranslate\">forEach<\/code> \u51fd\u6570\u7684\u7c7b\u578b\uff0c\u4ee5\u53ca\u4f20\u5165\u7684\u6570\u7ec4\u7684\u7c7b\u578b\uff0c\u6700\u540e\u63a8\u65ad\u51fa\u4e86 <code class=\"notranslate\">s<\/code> \u7684\u7c7b\u578b\u3002<\/p>\n<p dir=\"auto\">\u8fd9\u4e2a\u8fc7\u7a0b\u88ab\u79f0\u4e3a<strong>\u4e0a\u4e0b\u6587\u63a8\u65ad\uff08contextual typing\uff09<\/strong>\uff0c\u56e0\u4e3a\u6b63\u662f\u4ece\u51fd\u6570\u51fa\u73b0\u7684\u4e0a\u4e0b\u6587\u4e2d\u63a8\u65ad\u51fa\u4e86\u5b83\u5e94\u8be5\u6709\u7684\u7c7b\u578b\u3002<\/p>\n<p dir=\"auto\">\u8ddf\u63a8\u65ad\u89c4\u5219\u4e00\u6837\uff0c\u4f60\u4e5f\u4e0d\u9700\u8981\u5b66\u4e60\u5b83\u662f\u5982\u4f55\u53d1\u751f\u7684\uff0c\u53ea\u8981\u77e5\u9053\uff0c\u5b83\u786e\u5b9e\u5b58\u5728\u5e76\u5e2e\u52a9\u4f60\u7701\u6389\u67d0\u4e9b\u5e76\u4e0d\u9700\u8981\u7684\u6ce8\u89e3\u3002\u540e\u9762\uff0c\u6211\u4eec\u8fd8\u4f1a\u770b\u5230\u66f4\u591a\u8fd9\u6837\u7684\u4f8b\u5b50\uff0c\u4e86\u89e3\u4e00\u4e2a\u503c\u51fa\u73b0\u7684\u4e0a\u4e0b\u6587\u662f\u5982\u4f55\u5f71\u54cd\u5b83\u7684\u7c7b\u578b\u7684\u3002<\/p>\n<h2 dir=\"auto\">\u5bf9\u8c61\u7c7b\u578b\uff08Object Types\uff09<\/h2>\n<p dir=\"auto\">\u9664\u4e86\u539f\u59cb\u7c7b\u578b\uff0c\u6700\u5e38\u89c1\u7684\u7c7b\u578b\u5c31\u662f\u5bf9\u8c61\u7c7b\u578b\u4e86\u3002\u5b9a\u4e49\u4e00\u4e2a\u5bf9\u8c61\u7c7b\u578b\uff0c\u6211\u4eec\u53ea\u9700\u8981\u7b80\u5355\u7684\u5217\u51fa\u5b83\u7684\u5c5e\u6027\u548c\u5bf9\u5e94\u7684\u7c7b\u578b\u3002<\/p>\n<p dir=\"auto\">\u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"\/\/ The parameter's type annotation is an object type\nfunction printCoord(pt: { x: number; y: number }) {\n  console.log(&quot;The coordinate's x value is &quot; + pt.x);\n  console.log(&quot;The coordinate's y value is &quot; + pt.y);\n}\nprintCoord({ x: 3, y: 7 });\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c\">\/\/ The parameter's type annotation is an object type<\/span>\n<span class=\"pl-k\">function<\/span> <span class=\"pl-en\">printCoord<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">pt<\/span>: <span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">x<\/span>: <span class=\"pl-smi\">number<\/span><span class=\"pl-kos\">;<\/span> <span class=\"pl-c1\">y<\/span>: <span class=\"pl-smi\">number<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"The coordinate's x value is \"<\/span> <span class=\"pl-c1\">+<\/span> <span class=\"pl-s1\">pt<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">x<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"The coordinate's y value is \"<\/span> <span class=\"pl-c1\">+<\/span> <span class=\"pl-s1\">pt<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">y<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span>\n<span class=\"pl-en\">printCoord<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">x<\/span>: <span class=\"pl-c1\">3<\/span><span class=\"pl-kos\">,<\/span> <span class=\"pl-c1\">y<\/span>: <span class=\"pl-c1\">7<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u8fd9\u91cc\uff0c\u6211\u4eec\u7ed9\u53c2\u6570\u6dfb\u52a0\u4e86\u4e00\u4e2a\u7c7b\u578b\uff0c\u8be5\u7c7b\u578b\u6709\u4e24\u4e2a\u5c5e\u6027, <code class=\"notranslate\">x<\/code> \u548c <code class=\"notranslate\">y<\/code>\uff0c\u4e24\u4e2a\u90fd\u662f <code class=\"notranslate\">number<\/code> \u7c7b\u578b\u3002\u4f60\u53ef\u4ee5\u4f7f\u7528 <code class=\"notranslate\">,<\/code> \u6216\u8005 <code class=\"notranslate\">;<\/code>  \u5206\u5f00\u5c5e\u6027\uff0c\u6700\u540e\u4e00\u4e2a\u5c5e\u6027\u7684\u5206\u9694\u7b26\u52a0\u4e0d\u52a0\u90fd\u884c\u3002<\/p>\n<p dir=\"auto\">\u6bcf\u4e2a\u5c5e\u6027\u5bf9\u5e94\u7684\u7c7b\u578b\u662f\u53ef\u9009\u7684\uff0c\u5982\u679c\u4f60\u4e0d\u6307\u5b9a\uff0c\u9ed8\u8ba4\u4f7f\u7528 <code class=\"notranslate\">any<\/code> \u7c7b\u578b\u3002<\/p>\n<h3 dir=\"auto\">\u53ef\u9009\u5c5e\u6027\uff08Optional Properties\uff09<\/h3>\n<p dir=\"auto\">\u5bf9\u8c61\u7c7b\u578b\u53ef\u4ee5\u6307\u5b9a\u4e00\u4e9b\u751a\u81f3\u6240\u6709\u7684\u5c5e\u6027\u4e3a\u53ef\u9009\u7684\uff0c\u4f60\u53ea\u9700\u8981\u5728\u5c5e\u6027\u540d\u540e\u6dfb\u52a0\u4e00\u4e2a <code class=\"notranslate\">?<\/code> \uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content='function printName(obj: { first: string; last?: string }) {\n  \/\/ ...\n}\n\/\/ Both OK\nprintName({ first: \"Bob\" });\nprintName({ first: \"Alice\", last: \"Alisson\" });'><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">printName<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">obj<\/span>: <span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">first<\/span>: <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">;<\/span> <span class=\"pl-c1\">last<\/span>?: <span class=\"pl-smi\">string<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-c\">\/\/ ...<\/span>\n<span class=\"pl-kos\">}<\/span>\n<span class=\"pl-c\">\/\/ Both OK<\/span>\n<span class=\"pl-en\">printName<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">first<\/span>: <span class=\"pl-s\">\"Bob\"<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-en\">printName<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">first<\/span>: <span class=\"pl-s\">\"Alice\"<\/span><span class=\"pl-kos\">,<\/span> <span class=\"pl-c1\">last<\/span>: <span class=\"pl-s\">\"Alisson\"<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u5728 JavaScript \u4e2d\uff0c\u5982\u679c\u4f60\u83b7\u53d6\u4e00\u4e2a\u4e0d\u5b58\u5728\u7684\u5c5e\u6027\uff0c\u4f60\u4f1a\u5f97\u5230\u4e00\u4e2a <code class=\"notranslate\">undefined<\/code> \u800c\u4e0d\u662f\u4e00\u4e2a\u8fd0\u884c\u65f6\u9519\u8bef\u3002\u56e0\u6b64\uff0c\u5f53\u4f60\u83b7\u53d6\u4e00\u4e2a\u53ef\u9009\u5c5e\u6027\u65f6\uff0c\u4f60\u9700\u8981\u5728\u4f7f\u7528\u5b83\u524d\uff0c\u5148\u68c0\u67e5\u4e00\u4e0b\u662f\u5426\u662f <code class=\"notranslate\">undefined<\/code>\u3002<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function printName(obj: { first: string; last?: string }) {\n  \/\/ Error - might crash if 'obj.last' wasn't provided!\n  console.log(obj.last.toUpperCase());\n  \/\/ Object is possibly 'undefined'.\n  if (obj.last !== undefined) {\n    \/\/ OK\n    console.log(obj.last.toUpperCase());\n  }\n \n  \/\/ A safe alternative using modern JavaScript syntax:\n  console.log(obj.last?.toUpperCase());\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">printName<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">obj<\/span>: <span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">first<\/span>: <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">;<\/span> <span class=\"pl-c1\">last<\/span>?: <span class=\"pl-smi\">string<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-c\">\/\/ Error - might crash if 'obj.last' wasn't provided!<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">obj<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">last<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">toUpperCase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-c\">\/\/ Object is possibly 'undefined'.<\/span>\n  <span class=\"pl-k\">if<\/span> <span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">obj<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">last<\/span> <span class=\"pl-c1\">!==<\/span> <span class=\"pl-c1\">undefined<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c\">\/\/ OK<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">obj<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">last<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">toUpperCase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-kos\">}<\/span>\n \n  <span class=\"pl-c\">\/\/ A safe alternative using modern JavaScript syntax:<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">obj<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">last<\/span><span class=\"pl-kos\">?.<\/span><span class=\"pl-en\">toUpperCase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<h2 dir=\"auto\">\u8054\u5408\u7c7b\u578b\uff08Union Types\uff09<\/h2>\n<p dir=\"auto\">TypeScript \u7c7b\u578b\u7cfb\u7edf\u5141\u8bb8\u4f60\u4f7f\u7528\u4e00\u7cfb\u5217\u7684\u64cd\u4f5c\u7b26\uff0c\u57fa\u4e8e\u5df2\u7ecf\u5b58\u5728\u7684\u7c7b\u578b\u6784\u5efa\u65b0\u7684\u7c7b\u578b\u3002\u73b0\u5728\u6211\u4eec\u77e5\u9053\u5982\u4f55\u7f16\u5199\u4e00\u4e9b\u57fa\u7840\u7684\u7c7b\u578b\u4e86\uff0c\u662f\u65f6\u5019\u628a\u5b83\u4eec\u7ec4\u5408\u5728\u4e00\u8d77\u4e86\u3002<\/p>\n<h3 dir=\"auto\">\u5b9a\u4e49\u4e00\u4e2a\u8054\u5408\u7c7b\u578b\uff08Defining a Union Type\uff09<\/h3>\n<p dir=\"auto\">\u7b2c\u4e00\u79cd\u7ec4\u5408\u7c7b\u578b\u7684\u65b9\u5f0f\u662f\u4f7f\u7528\u8054\u5408\u7c7b\u578b\uff0c\u4e00\u4e2a\u8054\u5408\u7c7b\u578b\u662f\u7531\u4e24\u4e2a\u6216\u8005\u66f4\u591a\u7c7b\u578b\u7ec4\u6210\u7684\u7c7b\u578b\uff0c\u8868\u793a\u503c\u53ef\u80fd\u662f\u8fd9\u4e9b\u7c7b\u578b\u4e2d\u7684\u4efb\u610f\u4e00\u4e2a\u3002\u8fd9\u5176\u4e2d\u6bcf\u4e2a\u7c7b\u578b\u90fd\u662f\u8054\u5408\u7c7b\u578b\u7684<strong>\u6210\u5458\uff08members\uff09<\/strong>\u3002<\/p>\n<p dir=\"auto\">\u8ba9\u6211\u4eec\u5199\u4e00\u4e2a\u51fd\u6570\uff0c\u7528\u6765\u5904\u7406\u5b57\u7b26\u4e32\u6216\u8005\u6570\u5b57\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function printId(id: number | string) {\n  console.log(&quot;Your ID is: &quot; + id);\n}\n\/\/ OK\nprintId(101);\n\/\/ OK\nprintId(&quot;202&quot;);\n\/\/ Error\nprintId({ myID: 22342 });\n\/\/ Argument of type '{ myID: number; }' is not assignable to parameter of type 'string | number'.\n\/\/ Type '{ myID: number; }' is not assignable to type 'number'.\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">printId<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">id<\/span>: <span class=\"pl-smi\">number<\/span> <span class=\"pl-c1\">|<\/span> <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"Your ID is: \"<\/span> <span class=\"pl-c1\">+<\/span> <span class=\"pl-s1\">id<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span>\n<span class=\"pl-c\">\/\/ OK<\/span>\n<span class=\"pl-en\">printId<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-c1\">101<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-c\">\/\/ OK<\/span>\n<span class=\"pl-en\">printId<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"202\"<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-c\">\/\/ Error<\/span>\n<span class=\"pl-en\">printId<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">{<\/span> <span class=\"pl-c1\">myID<\/span>: <span class=\"pl-c1\">22342<\/span> <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-c\">\/\/ Argument of type '{ myID: number; }' is not assignable to parameter of type 'string | number'.<\/span>\n<span class=\"pl-c\">\/\/ Type '{ myID: number; }' is not assignable to type 'number'.<\/span><\/pre>\n<\/div>\n<h3 dir=\"auto\">\u4f7f\u7528\u8054\u5408\u7c7b\u578b\uff08Working with Union Types\uff09<\/h3>\n<p dir=\"auto\">\u63d0\u4f9b\u4e00\u4e2a\u7b26\u5408\u8054\u5408\u7c7b\u578b\u7684\u503c\u5f88\u5bb9\u6613\uff0c\u4f60\u53ea\u9700\u8981\u63d0\u4f9b\u7b26\u5408\u4efb\u610f\u4e00\u4e2a\u8054\u5408\u6210\u5458\u7c7b\u578b\u7684\u503c\u5373\u53ef\u3002\u90a3\u4e48\u5728\u4f60\u6709\u4e86\u4e00\u4e2a\u8054\u5408\u7c7b\u578b\u7684\u503c\u540e\uff0c\u4f60\u8be5\u600e\u6837\u4f7f\u7528\u5b83\u5462\uff1f<\/p>\n<p dir=\"auto\">TypeScript \u4f1a\u8981\u6c42\u4f60\u505a\u7684\u4e8b\u60c5\uff0c\u5fc5\u987b\u5bf9\u6bcf\u4e2a\u8054\u5408\u7684\u6210\u5458\u90fd\u662f\u6709\u6548\u7684\u3002\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u5982\u679c\u4f60\u6709\u4e00\u4e2a\u8054\u5408\u7c7b\u578b <code class=\"notranslate\">string | number<\/code> , \u4f60\u4e0d\u80fd\u4f7f\u7528\u53ea\u5b58\u5728 <code class=\"notranslate\">string<\/code> \u4e0a\u7684\u65b9\u6cd5\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function printId(id: number | string) {\n  console.log(id.toUpperCase());\n    \/\/ Property 'toUpperCase' does not exist on type 'string | number'.\n    \/\/ Property 'toUpperCase' does not exist on type 'number'.\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">printId<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">id<\/span>: <span class=\"pl-smi\">number<\/span> <span class=\"pl-c1\">|<\/span> <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">id<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">toUpperCase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n    <span class=\"pl-c\">\/\/ Property 'toUpperCase' does not exist on type 'string | number'.<\/span>\n    <span class=\"pl-c\">\/\/ Property 'toUpperCase' does not exist on type 'number'.<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u89e3\u51b3\u65b9\u6848\u662f\u7528\u4ee3\u7801\u6536\u7a84\u8054\u5408\u7c7b\u578b\uff0c\u5c31\u50cf\u4f60\u5728 JavaScript \u6ca1\u6709\u7c7b\u578b\u6ce8\u89e3\u90a3\u6837\u4f7f\u7528\u3002\u5f53 TypeScript \u53ef\u4ee5\u6839\u636e\u4ee3\u7801\u7684\u7ed3\u6784\u63a8\u65ad\u51fa\u4e00\u4e2a\u66f4\u52a0\u5177\u4f53\u7684\u7c7b\u578b\u65f6\uff0c\u7c7b\u578b\u6536\u7a84\u5c31\u4f1a\u51fa\u73b0\u3002<\/p>\n<p dir=\"auto\">\u4e3e\u4e2a\u4f8b\u5b50\uff0cTypeScript \u77e5\u9053\uff0c\u5bf9\u4e00\u4e2a <code class=\"notranslate\">string<\/code> \u7c7b\u578b\u7684\u503c\u4f7f\u7528 <code class=\"notranslate\">typeof<\/code> \u4f1a\u8fd4\u56de\u5b57\u7b26\u4e32 <code class=\"notranslate\">\"string\"<\/code>\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function printId(id: number | string) {\n  if (typeof id === &quot;string&quot;) {\n    \/\/ In this branch, id is of type 'string'\n    console.log(id.toUpperCase());\n  } else {\n    \/\/ Here, id is of type 'number'\n    console.log(id);\n  }\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">printId<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">id<\/span>: <span class=\"pl-smi\">number<\/span> <span class=\"pl-c1\">|<\/span> <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-k\">if<\/span> <span class=\"pl-kos\">(<\/span><span class=\"pl-k\">typeof<\/span> <span class=\"pl-s1\">id<\/span> <span class=\"pl-c1\">===<\/span> <span class=\"pl-s\">\"string\"<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c\">\/\/ In this branch, id is of type 'string'<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">id<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">toUpperCase<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-kos\">}<\/span> <span class=\"pl-k\">else<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c\">\/\/ Here, id is of type 'number'<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">id<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-kos\">}<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u518d\u4e3e\u4e00\u4e2a\u4f8b\u5b50\uff0c\u4f7f\u7528\u51fd\u6570\uff0c\u6bd4\u5982 <code class=\"notranslate\">Array.isArray<\/code>:<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function welcomePeople(x: string[] | string) {\n  if (Array.isArray(x)) {\n    \/\/ Here: 'x' is 'string[]'\n    console.log(&quot;Hello, &quot; + x.join(&quot; and &quot;));\n  } else {\n    \/\/ Here: 'x' is 'string'\n    console.log(&quot;Welcome lone traveler &quot; + x);\n  }\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">welcomePeople<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">x<\/span>: <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">[<\/span><span class=\"pl-kos\">]<\/span> <span class=\"pl-c1\">|<\/span> <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-k\">if<\/span> <span class=\"pl-kos\">(<\/span><span class=\"pl-smi\">Array<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">isArray<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">x<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c\">\/\/ Here: 'x' is 'string[]'<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"Hello, \"<\/span> <span class=\"pl-c1\">+<\/span> <span class=\"pl-s1\">x<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">join<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\" and \"<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-kos\">}<\/span> <span class=\"pl-k\">else<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c\">\/\/ Here: 'x' is 'string'<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"Welcome lone traveler \"<\/span> <span class=\"pl-c1\">+<\/span> <span class=\"pl-s1\">x<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-kos\">}<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u6ce8\u610f\u5728 <code class=\"notranslate\">else<\/code>\u5206\u652f\uff0c\u6211\u4eec\u5e76\u4e0d\u9700\u8981\u505a\u4efb\u4f55\u7279\u6b8a\u7684\u4e8b\u60c5\uff0c\u5982\u679c <code class=\"notranslate\">x<\/code> \u4e0d\u662f <code class=\"notranslate\">string[]<\/code>\uff0c\u90a3\u4e48\u5b83\u4e00\u5b9a\u662f <code class=\"notranslate\">string<\/code> .<\/p>\n<p dir=\"auto\">\u6709\u65f6\u5019\uff0c\u5982\u679c\u8054\u5408\u7c7b\u578b\u91cc\u7684\u6bcf\u4e2a\u6210\u5458\u90fd\u6709\u4e00\u4e2a\u5c5e\u6027\uff0c\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u6570\u7ec4\u548c\u5b57\u7b26\u4e32\u90fd\u6709 <code class=\"notranslate\">slice<\/code> \u65b9\u6cd5\uff0c\u4f60\u5c31\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528\u8fd9\u4e2a\u5c5e\u6027\uff0c\u800c\u4e0d\u7528\u505a\u7c7b\u578b\u6536\u7a84\uff1a<\/p>\n<div class=\"highlight highlight-source-ts notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"\/\/ Return type is inferred as number[] | string\nfunction getFirstThree(x: number[] | string) {\n  return x.slice(0, 3);\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c\">\/\/ Return type is inferred as number[] | string<\/span>\n<span class=\"pl-k\">function<\/span> <span class=\"pl-en\">getFirstThree<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">x<\/span>: <span class=\"pl-smi\">number<\/span><span class=\"pl-kos\">[<\/span><span class=\"pl-kos\">]<\/span> <span class=\"pl-c1\">|<\/span> <span class=\"pl-smi\">string<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-k\">return<\/span> <span class=\"pl-s1\">x<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">slice<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-c1\">0<\/span><span class=\"pl-kos\">,<\/span> <span class=\"pl-c1\">3<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<blockquote>\n<p dir=\"auto\">\u4f60\u53ef\u80fd\u5f88\u5947\u602a\uff0c\u4e3a\u4ec0\u4e48\u8054\u5408\u7c7b\u578b\u53ea\u80fd\u4f7f\u7528\u8fd9\u4e9b\u7c7b\u578b\u5c5e\u6027\u7684\u4ea4\u96c6\uff0c\u8ba9\u6211\u4eec\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u73b0\u5728\u6709\u4e24\u4e2a\u623f\u95f4\uff0c\u4e00\u4e2a\u623f\u95f4\u90fd\u662f\u8eab\u9ad8\u516b\u5c3a\u6234\u5e3d\u5b50\u7684\u4eba\uff0c\u53e6\u5916\u4e00\u4e2a\u623f\u95f4\u5219\u662f\u4f1a\u8bb2\u897f\u73ed\u7259\u8bed\u6234\u5e3d\u5b50\u7684\u4eba\uff0c\u5408\u5e76\u8fd9\u4e24\u4e2a\u623f\u95f4\u540e\uff0c\u6211\u4eec\u552f\u4e00\u77e5\u9053\u7684\u4e8b\u60c5\u662f\uff1a\u6bcf\u4e00\u4e2a\u4eba\u90fd\u6234\u7740\u5e3d\u5b50\u3002<\/p>\n<\/blockquote>\n<h2 dir=\"auto\">TypeScript \u7cfb\u5217<\/h2>\n<p dir=\"auto\">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<a href=\"http:\/\/ts.yayujs.com\/\" rel=\"nofollow\">\u70b9\u6b64\u6d4f\u89c8\u5168\u7cfb\u5217\u6587\u7ae0\uff0c\u5e76\u5efa\u8bae\u987a\u4fbf\u6536\u85cf\u7ad9\u70b9\u3002<\/a><\/p>\n<p dir=\"auto\">\u5fae\u4fe1\uff1a\u300cmqyqingfeng\u300d\uff0c\u52a0\u6211\u8fdb\u51b4\u7fbd\u552f\u4e00\u7684\u8bfb\u8005\u7fa4\u3002<\/p>\n<\/td>\n<p>\u6587\u7ae0\u8f6c\u8f7d\u81ea<a href='https:\/\/github.com\/mqyqingfeng\/Blog\/issues\/228'>https:\/\/github.com\/mqyqingfeng\/Blog\/issues\/228<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>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\u7ffb\u8bd1\u6574\u7406\u81ea Ty&#8230;<\/p>\n<p class=\"read-more\"><a class=\"btn btn-default\" href=\"https:\/\/www.lccc.top\/?p=1416\"> Read More<span class=\"screen-reader-text\">  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-1416","post","type-post","status-publish","format-standard","hentry","category-learn"],"_links":{"self":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1416"}],"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=1416"}],"version-history":[{"count":1,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1416\/revisions"}],"predecessor-version":[{"id":2398,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1416\/revisions\/2398"}],"wp:attachment":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1416"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1416"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1416"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}