{"id":1353,"date":"2024-06-02T22:21:25","date_gmt":"2024-06-02T22:21:25","guid":{"rendered":""},"modified":"2024-06-05T03:08:19","modified_gmt":"2024-06-04T19:08:19","slug":"es6-%e5%ae%8c%e5%85%a8%e4%bd%bf%e7%94%a8%e6%89%8b%e5%86%8c","status":"publish","type":"post","link":"https:\/\/www.lccc.top\/?p=1353","title":{"rendered":"ES6 \u5b8c\u5168\u4f7f\u7528\u624b\u518c"},"content":{"rendered":"\n

\u524d\u8a00<\/h2>\n
    \n
  1. \u8fd9\u91cc\u7684 “ES6” \u6cdb\u6307 ES5 \u4e4b\u540e\u7684\u65b0\u8bed\u6cd5<\/li>\n
  2. \u8fd9\u91cc\u7684 “\u5b8c\u5168” \u662f\u6307\u672c\u6587\u5c3d\u53ef\u80fd\u9f50\u5168<\/li>\n
  3. \u8fd9\u91cc\u7684 “\u4f7f\u7528” \u662f\u6307\u672c\u6587\u4f1a\u5c55\u793a\u5f88\u591a ES6 \u7684\u4f7f\u7528\u573a\u666f<\/li>\n
  4. \u8fd9\u91cc\u7684 “\u624b\u518c” \u662f\u6307\u4f60\u53ef\u4ee5\u53c2\u7167\u672c\u6587\u5c06\u9879\u76ee\u66f4\u591a\u7684\u91cd\u6784\u4e3a ES6 \u8bed\u6cd5<\/li>\n<\/ol>\n

    \u6b64\u5916\u8fd8\u8981\u6ce8\u610f\u8fd9\u91cc\u4e0d\u4e00\u5b9a\u5c31\u662f\u6b63\u5f0f\u8fdb\u5165\u89c4\u8303\u7684\u8bed\u6cd5\u3002<\/p>\n

    1. let \u548c const<\/h2>\n

    \u5728\u6211\u4eec\u5f00\u53d1\u7684\u65f6\u5019\uff0c\u53ef\u80fd\u8ba4\u4e3a\u5e94\u8be5\u9ed8\u8ba4\u4f7f\u7528 let \u800c\u4e0d\u662f var\uff0c\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u5bf9\u4e8e\u9700\u8981\u5199\u4fdd\u62a4\u7684\u53d8\u91cf\u8981\u4f7f\u7528 const\u3002<\/p>\n

    \u7136\u800c\u53e6\u4e00\u79cd\u505a\u6cd5\u65e5\u76ca\u666e\u53ca\uff1a\u9ed8\u8ba4\u4f7f\u7528 const\uff0c\u53ea\u6709\u5f53\u786e\u5b9e\u9700\u8981\u6539\u53d8\u53d8\u91cf\u7684\u503c\u7684\u65f6\u5019\u624d\u4f7f\u7528 let\u3002\u8fd9\u662f\u56e0\u4e3a\u5927\u90e8\u5206\u7684\u53d8\u91cf\u7684\u503c\u5728\u521d\u59cb\u5316\u540e\u4e0d\u5e94\u518d\u6539\u53d8\uff0c\u800c\u9884\u6599\u4e4b\u5916\u7684\u53d8\u91cf\u7684\u4fee\u6539\u662f\u5f88\u591a bug \u7684\u6e90\u5934\u3002<\/p>\n

    <\/p>\n
    \/\/ \u4f8b\u5b50 1-1<\/span>\n\n\/\/ bad<\/span>\nvar<\/span> foo<\/span> =<\/span> 'bar'<\/span>;<\/span>\n\n\/\/ good<\/span>\nlet<\/span> foo<\/span> =<\/span> 'bar'<\/span>;<\/span>\n\n\/\/ better<\/span>\nconst<\/span> foo<\/span> =<\/span> 'bar'<\/span>;<\/span><\/pre>\n<\/div>\n
    2. \u6a21\u677f\u5b57\u7b26\u4e32<\/h2>\n
    1. \u6a21\u677f\u5b57\u7b26\u4e32<\/h3>\n
    \u9700\u8981\u62fc\u63a5\u5b57\u7b26\u4e32\u7684\u65f6\u5019\u5c3d\u91cf\u6539\u6210\u4f7f\u7528\u6a21\u677f\u5b57\u7b26\u4e32:<\/p>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 2-1<\/span>\n\n\/\/ bad<\/span>\nconst<\/span> foo<\/span> =<\/span> 'this is a'<\/span> +<\/span> example<\/span>;<\/span>\n\n\/\/ good<\/span>\nconst<\/span> foo<\/span> =<\/span> `this is a ${<\/span>example<\/span>}<\/span><\/span>`<\/span>;<\/span><\/pre>\n<\/div>\n
    2. \u6807\u7b7e\u6a21\u677f<\/h3>\n
    \u53ef\u4ee5\u501f\u52a9\u6807\u7b7e\u6a21\u677f\u4f18\u5316\u4e66\u5199\u65b9\u5f0f:<\/p>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 2-2<\/span>\n\nlet<\/span> url<\/span> =<\/span> oneLine<\/span> `<\/span>\n    www.taobao.com\/example\/index.html<\/span>\n    ?foo=${<\/span>foo<\/span>}<\/span><\/span><\/span>\n    &bar=${<\/span>bar<\/span>}<\/span><\/span><\/span>\n`<\/span>;<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>url<\/span>)<\/span>;<\/span> \/\/ www.taobao.com\/example\/index.html?foo=foo&bar=bar<\/span><\/pre>\n<\/div>\n
    oneLine \u7684\u6e90\u7801\u53ef\u4ee5\u53c2\u8003 \u300aES6 \u7cfb\u5217\u4e4b\u6a21\u677f\u5b57\u7b26\u4e32\u300b<\/a><\/p>\n
    3. \u7bad\u5934\u51fd\u6570<\/h2>\n
    \u4f18\u5148\u4f7f\u7528\u7bad\u5934\u51fd\u6570\uff0c\u4e0d\u8fc7\u4ee5\u4e0b\u51e0\u79cd\u60c5\u51b5\u907f\u514d\u4f7f\u7528\uff1a<\/p>\n
    1. \u4f7f\u7528\u7bad\u5934\u51fd\u6570\u5b9a\u4e49\u5bf9\u8c61\u7684\u65b9\u6cd5<\/h3>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 3-1<\/span>\n\n\/\/ bad<\/span>\nlet<\/span> foo<\/span> =<\/span> {<\/span>\n  value<\/span>: 1<\/span>,<\/span>\n  getValue<\/span>: (<\/span>)<\/span> =><\/span> console<\/span>.<\/span>log<\/span>(<\/span>this<\/span>.<\/span>value<\/span>)<\/span>\n}<\/span>\n\nfoo<\/span>.<\/span>getValue<\/span>(<\/span>)<\/span>;<\/span>  \/\/ undefined<\/span><\/pre>\n<\/div>\n
    2. \u5b9a\u4e49\u539f\u578b\u65b9\u6cd5<\/h3>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 3-2<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> Foo<\/span>(<\/span>)<\/span> {<\/span>\n  this<\/span>.<\/span>value<\/span> =<\/span> 1<\/span>\n}<\/span>\n\nFoo<\/span>.<\/span>prototype<\/span>.<\/span>getValue<\/span> =<\/span> (<\/span>)<\/span> =><\/span> console<\/span>.<\/span>log<\/span>(<\/span>this<\/span>.<\/span>value<\/span>)<\/span>\n\nlet<\/span> foo<\/span> =<\/span> new<\/span> Foo<\/span>(<\/span>)<\/span>\nfoo<\/span>.<\/span>getValue<\/span>(<\/span>)<\/span>;<\/span>  \/\/ undefined<\/span><\/pre>\n<\/div>\n
    3. \u4f5c\u4e3a\u4e8b\u4ef6\u7684\u56de\u8c03\u51fd\u6570<\/h3>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 3-3<\/span>\n\n\/\/ bad<\/span>\nconst<\/span> button<\/span> =<\/span> document<\/span>.<\/span>getElementById<\/span>(<\/span>'myButton'<\/span>)<\/span>;<\/span>\nbutton<\/span>.<\/span>addEventListener<\/span>(<\/span>'click'<\/span>,<\/span> (<\/span>)<\/span> =><\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>this<\/span> ===<\/span> window<\/span>)<\/span>;<\/span> \/\/ => true<\/span>\n    this<\/span>.<\/span>innerHTML<\/span> =<\/span> 'Clicked button'<\/span>;<\/span>\n}<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
    4. Symbol<\/h2>\n
    1. \u552f\u4e00\u503c<\/h3>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 4-1<\/span>\n\n\n\/\/ bad<\/span>\n\/\/ 1. \u521b\u5efa\u7684\u5c5e\u6027\u4f1a\u88ab for-in \u6216 Object.keys() \u679a\u4e3e\u51fa\u6765<\/span>\n\/\/ 2. \u4e00\u4e9b\u5e93\u53ef\u80fd\u5728\u5c06\u6765\u4f1a\u4f7f\u7528\u540c\u6837\u7684\u65b9\u5f0f\uff0c\u8fd9\u4f1a\u4e0e\u4f60\u7684\u4ee3\u7801\u53d1\u751f\u51b2\u7a81<\/span>\nif<\/span> (<\/span>element<\/span>.<\/span>isMoving<\/span>)<\/span> {<\/span>\n  smoothAnimations<\/span>(<\/span>element<\/span>)<\/span>;<\/span>\n}<\/span>\nelement<\/span>.<\/span>isMoving<\/span> =<\/span> true<\/span>;<\/span>\n\n\/\/ good<\/span>\nif<\/span> (<\/span>element<\/span>.<\/span>__$jorendorff_animation_library$PLEASE_DO_NOT_USE_THIS_PROPERTY$isMoving__<\/span>)<\/span> {<\/span>\n  smoothAnimations<\/span>(<\/span>element<\/span>)<\/span>;<\/span>\n}<\/span>\nelement<\/span>.<\/span>__$jorendorff_animation_library$PLEASE_DO_NOT_USE_THIS_PROPERTY$isMoving__<\/span> =<\/span> true<\/span>;<\/span>\n\n\/\/ better<\/span>\nvar<\/span> isMoving<\/span> =<\/span> Symbol<\/span>(<\/span>\"isMoving\"<\/span>)<\/span>;<\/span>\n\n...\n\nif<\/span> (<\/span>element<\/span>[<\/span>isMoving<\/span>]<\/span>)<\/span> {<\/span>\n  smoothAnimations<\/span>(<\/span>element<\/span>)<\/span>;<\/span>\n}<\/span>\nelement<\/span>[<\/span>isMoving<\/span>]<\/span> =<\/span> true<\/span>;<\/span><\/pre>\n<\/div>\n
    2. \u9b54\u672f\u5b57\u7b26\u4e32<\/h3>\n
    \u9b54\u672f\u5b57\u7b26\u4e32\u6307\u7684\u662f\u5728\u4ee3\u7801\u4e4b\u4e2d\u591a\u6b21\u51fa\u73b0\u3001\u4e0e\u4ee3\u7801\u5f62\u6210\u5f3a\u8026\u5408\u7684\u67d0\u4e00\u4e2a\u5177\u4f53\u7684\u5b57\u7b26\u4e32\u6216\u8005\u6570\u503c\u3002<\/p>\n
    \u9b54\u672f\u5b57\u7b26\u4e32\u4e0d\u5229\u4e8e\u4fee\u6539\u548c\u7ef4\u62a4\uff0c\u98ce\u683c\u826f\u597d\u7684\u4ee3\u7801\uff0c\u5e94\u8be5\u5c3d\u91cf\u6d88\u9664\u9b54\u672f\u5b57\u7b26\u4e32\uff0c\u6539\u7531\u542b\u4e49\u6e05\u6670\u7684\u53d8\u91cf\u4ee3\u66ff\u3002<\/p>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 4-1<\/span>\n\n\/\/ bad<\/span>\nconst<\/span> TYPE_AUDIO<\/span> =<\/span> 'AUDIO'<\/span>\nconst<\/span> TYPE_VIDEO<\/span> =<\/span> 'VIDEO'<\/span>\nconst<\/span> TYPE_IMAGE<\/span> =<\/span> 'IMAGE'<\/span>\n\n\/\/ good<\/span>\nconst<\/span> TYPE_AUDIO<\/span> =<\/span> Symbol<\/span>(<\/span>)<\/span>\nconst<\/span> TYPE_VIDEO<\/span> =<\/span> Symbol<\/span>(<\/span>)<\/span>\nconst<\/span> TYPE_IMAGE<\/span> =<\/span> Symbol<\/span>(<\/span>)<\/span>\n\nfunction<\/span> handleFileResource<\/span>(<\/span>resource<\/span>)<\/span> {<\/span>\n  switch<\/span>(<\/span>resource<\/span>.<\/span>type<\/span>)<\/span> {<\/span>\n    case<\/span> TYPE_AUDIO<\/span>:\n      playAudio<\/span>(<\/span>resource<\/span>)<\/span>\n      break<\/span>\n    case<\/span> TYPE_VIDEO<\/span>:\n      playVideo<\/span>(<\/span>resource<\/span>)<\/span>\n      break<\/span>\n    case<\/span> TYPE_IMAGE<\/span>:\n      previewImage<\/span>(<\/span>resource<\/span>)<\/span>\n      break<\/span>\n    default<\/span>:\n      throw<\/span> new<\/span> Error<\/span>(<\/span>'Unknown type of resource'<\/span>)<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
    3. \u79c1\u6709\u53d8\u91cf<\/h3>\n
    Symbol \u4e5f\u53ef\u4ee5\u7528\u4e8e\u79c1\u6709\u53d8\u91cf\u7684\u5b9e\u73b0\u3002<\/p>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 4-3<\/span>\n\nconst<\/span> Example<\/span> =<\/span> (<\/span>function<\/span>(<\/span>)<\/span> {<\/span>\n    var<\/span> _private<\/span> =<\/span> Symbol<\/span>(<\/span>'private'<\/span>)<\/span>;<\/span>\n\n    class<\/span> Example<\/span> {<\/span>\n        constructor<\/span>(<\/span>)<\/span> {<\/span>\n          this<\/span>[<\/span>_private<\/span>]<\/span> =<\/span> 'private'<\/span>;<\/span>\n        }<\/span>\n        getName<\/span>(<\/span>)<\/span> {<\/span>\n          return<\/span> this<\/span>[<\/span>_private<\/span>]<\/span>;<\/span>\n        }<\/span>\n    }<\/span>\n\n    return<\/span> Example<\/span>;<\/span>\n}<\/span>)<\/span>(<\/span>)<\/span>;<\/span>\n\nvar<\/span> ex<\/span> =<\/span> new<\/span> Example<\/span>(<\/span>)<\/span>;<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>ex<\/span>.<\/span>getName<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ private<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>ex<\/span>.<\/span>name<\/span>)<\/span>;<\/span> \/\/ undefined<\/span><\/pre>\n<\/div>\n
    5. Set \u548c Map<\/h2>\n
    1. \u6570\u7ec4\u53bb\u91cd<\/h3>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 5-1<\/span>\n\n[<\/span>...new<\/span> Set<\/span>(<\/span>array<\/span>)<\/span>]<\/span><\/pre>\n<\/div>\n
    2. \u6761\u4ef6\u8bed\u53e5\u7684\u4f18\u5316<\/h3>\n
    <\/p>\n
    \/\/ \u4f8b\u5b50 5-2<\/span>\n\/\/ \u6839\u636e\u989c\u8272\u627e\u51fa\u5bf9\u5e94\u7684\u6c34\u679c<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> test<\/span>(<\/span>color<\/span>)<\/span> {<\/span>\n  switch<\/span> (<\/span>color<\/span>)<\/span> {<\/span>\n    case<\/span> 'red'<\/span>:\n      return<\/span> [<\/span>'apple'<\/span>,<\/span> 'strawberry'<\/span>]<\/span>;<\/span>\n    case<\/span> 'yellow'<\/span>:\n      return<\/span> [<\/span>'banana'<\/span>,<\/span> 'pineapple'<\/span>]<\/span>;<\/span>\n    case<\/span> 'purple'<\/span>:\n      return<\/span> [<\/span>'grape'<\/span>,<\/span> 'plum'<\/span>]<\/span>;<\/span>\n    default<\/span>:\n      return<\/span> [<\/span>]<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\ntest<\/span>(<\/span>'yellow'<\/span>)<\/span>;<\/span> \/\/ ['banana', 'pineapple']<\/span><\/pre>\n<\/div>\n
    <\/p>\n
    \/\/ good<\/span>\nconst<\/span> fruitColor<\/span> =<\/span> {<\/span>\n  red<\/span>: [<\/span>'apple'<\/span>,<\/span> 'strawberry'<\/span>]<\/span>,<\/span>\n  yellow<\/span>: [<\/span>'banana'<\/span>,<\/span> 'pineapple'<\/span>]<\/span>,<\/span>\n  purple<\/span>: [<\/span>'grape'<\/span>,<\/span> 'plum'<\/span>]<\/span>\n}<\/span>;<\/span>\n\nfunction<\/span> test<\/span>(<\/span>color<\/span>)<\/span> {<\/span>\n  return<\/span> fruitColor<\/span>[<\/span>color<\/span>]<\/span> ||<\/span> [<\/span>]<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
    <\/p>\n
    \/\/ better<\/span>\nconst<\/span> fruitColor<\/span> =<\/span> new<\/span> Map<\/span>(<\/span>)<\/span>\n  .<\/span>set<\/span>(<\/span>'red'<\/span>,<\/span> [<\/span>'apple'<\/span>,<\/span> 'strawberry'<\/span>]<\/span>)<\/span>\n  .<\/span>set<\/span>(<\/span>'yellow'<\/span>,<\/span> [<\/span>'banana'<\/span>,<\/span> 'pineapple'<\/span>]<\/span>)<\/span>\n  .<\/span>set<\/span>(<\/span>'purple'<\/span>,<\/span> [<\/span>'grape'<\/span>,<\/span> 'plum'<\/span>]<\/span>)<\/span>;<\/span>\n\nfunction<\/span> test<\/span>(<\/span>color<\/span>)<\/span> {<\/span>\n  return<\/span> fruitColor<\/span>.<\/span>get<\/span>(<\/span>color<\/span>)<\/span> ||<\/span> [<\/span>]<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
    6. for of<\/h2>\n
    1. \u904d\u5386\u8303\u56f4<\/h3>\n
    for…of \u5faa\u73af\u53ef\u4ee5\u4f7f\u7528\u7684\u8303\u56f4\u5305\u62ec\uff1a<\/p>\n
      \n
    1. \u6570\u7ec4<\/li>\n
    2. Set<\/li>\n
    3. Map<\/li>\n
    4. \u7c7b\u6570\u7ec4\u5bf9\u8c61\uff0c\u5982 arguments \u5bf9\u8c61\u3001DOM NodeList \u5bf9\u8c61<\/li>\n
    5. Generator \u5bf9\u8c61<\/li>\n
    6. \u5b57\u7b26\u4e32<\/li>\n<\/ol>\n
      2. \u4f18\u52bf<\/h3>\n
      ES2015 \u5f15\u5165\u4e86 for..of \u5faa\u73af\uff0c\u5b83\u7ed3\u5408\u4e86 forEach \u7684\u7b80\u6d01\u6027\u548c\u4e2d\u65ad\u5faa\u73af\u7684\u80fd\u529b\uff1a<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 6-1<\/span>\n\nfor<\/span> (<\/span>const<\/span> v<\/span> of<\/span> [<\/span>'a'<\/span>,<\/span> 'b'<\/span>,<\/span> 'c'<\/span>]<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>v<\/span>)<\/span>;<\/span>\n}<\/span>\n\/\/ a b c<\/span>\n\nfor<\/span> (<\/span>const<\/span> [<\/span>i<\/span>,<\/span> v<\/span>]<\/span> of<\/span> [<\/span>'a'<\/span>,<\/span> 'b'<\/span>,<\/span> 'c'<\/span>]<\/span>.<\/span>entries<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>i<\/span>,<\/span> v<\/span>)<\/span>;<\/span>\n}<\/span>\n\/\/ 0 \"a\"<\/span>\n\/\/ 1 \"b\"<\/span>\n\/\/ 2 \"c\"<\/span><\/pre>\n<\/div>\n
      3. \u904d\u5386 Map<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 6-2<\/span>\n\nlet<\/span> map<\/span> =<\/span> new<\/span> Map<\/span>(<\/span>arr<\/span>)<\/span>;<\/span>\n\n\/\/ \u904d\u5386 key \u503c<\/span>\nfor<\/span> (<\/span>let<\/span> key<\/span> of<\/span> map<\/span>.<\/span>keys<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>key<\/span>)<\/span>;<\/span>\n}<\/span>\n\n\/\/ \u904d\u5386 value \u503c<\/span>\nfor<\/span> (<\/span>let<\/span> value<\/span> of<\/span> map<\/span>.<\/span>values<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>value<\/span>)<\/span>;<\/span>\n}<\/span>\n\n\/\/ \u904d\u5386 key \u548c value \u503c(\u4e00)<\/span>\nfor<\/span> (<\/span>let<\/span> item<\/span> of<\/span> map<\/span>.<\/span>entries<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>item<\/span>[<\/span>0<\/span>]<\/span>,<\/span> item<\/span>[<\/span>1<\/span>]<\/span>)<\/span>;<\/span>\n}<\/span>\n\n\/\/ \u904d\u5386 key \u548c value \u503c(\u4e8c)<\/span>\nfor<\/span> (<\/span>let<\/span> [<\/span>key<\/span>,<\/span> value<\/span>]<\/span> of<\/span> data<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>key<\/span>)<\/span>\n}<\/span><\/pre>\n<\/div>\n
      7. Promise<\/h2>\n
      1. \u57fa\u672c\u793a\u4f8b<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 7-1<\/span>\n\n\/\/ bad<\/span>\nrequest<\/span>(<\/span>url<\/span>,<\/span> function<\/span>(<\/span>err<\/span>,<\/span> res<\/span>,<\/span> body<\/span>)<\/span> {<\/span>\n    if<\/span> (<\/span>err<\/span>)<\/span> handleError<\/span>(<\/span>err<\/span>)<\/span>;<\/span>\n    fs<\/span>.<\/span>writeFile<\/span>(<\/span>'1.txt'<\/span>,<\/span> body<\/span>,<\/span> function<\/span>(<\/span>err<\/span>)<\/span> {<\/span>\n        request<\/span>(<\/span>url2<\/span>,<\/span> function<\/span>(<\/span>err<\/span>,<\/span> res<\/span>,<\/span> body<\/span>)<\/span> {<\/span>\n            if<\/span> (<\/span>err<\/span>)<\/span> handleError<\/span>(<\/span>err<\/span>)<\/span>\n        }<\/span>)<\/span>\n    }<\/span>)<\/span>\n}<\/span>)<\/span>;<\/span>\n\n\/\/ good<\/span>\nrequest<\/span>(<\/span>url<\/span>)<\/span>\n.<\/span>then<\/span>(<\/span>function<\/span>(<\/span>result<\/span>)<\/span> {<\/span>\n    return<\/span> writeFileAsynv<\/span>(<\/span>'1.txt'<\/span>,<\/span> result<\/span>)<\/span>\n}<\/span>)<\/span>\n.<\/span>then<\/span>(<\/span>function<\/span>(<\/span>result<\/span>)<\/span> {<\/span>\n    return<\/span> request<\/span>(<\/span>url2<\/span>)<\/span>\n}<\/span>)<\/span>\n.<\/span>catch<\/span>(<\/span>function<\/span>(<\/span>e<\/span>)<\/span>{<\/span>\n    handleError<\/span>(<\/span>e<\/span>)<\/span>\n}<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      2. finally<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 7-2<\/span>\n\nfetch<\/span>(<\/span>'file.json'<\/span>)<\/span>\n.<\/span>then<\/span>(<\/span>data<\/span> =><\/span> data<\/span>.<\/span>json<\/span>(<\/span>)<\/span>)<\/span>\n.<\/span>catch<\/span>(<\/span>error<\/span> =><\/span> console<\/span>.<\/span>error<\/span>(<\/span>error<\/span>)<\/span>)<\/span>\n.<\/span>finally<\/span>(<\/span>(<\/span>)<\/span> =><\/span> console<\/span>.<\/span>log<\/span>(<\/span>'finished'<\/span>)<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      8. Async<\/h2>\n
      1. \u4ee3\u7801\u66f4\u52a0\u7b80\u6d01<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 8-1<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  return<\/span> (<\/span>\n    fetchData<\/span>(<\/span>)<\/span>\n    .<\/span>then<\/span>(<\/span>(<\/span>)<\/span> =><\/span> {<\/span>\n      return<\/span> \"done\"<\/span>\n    }<\/span>)<\/span>;<\/span>\n  )<\/span>\n}<\/span>\n\n\/\/ better<\/span>\nasync<\/span> function<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  await<\/span> fetchData<\/span>(<\/span>)<\/span>\n  return<\/span> \"done\"<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 8-2<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  return<\/span> fetchData<\/span>(<\/span>)<\/span>\n  .<\/span>then<\/span>(<\/span>data<\/span> =><\/span> {<\/span>\n    if<\/span> (<\/span>data<\/span>.<\/span>moreData<\/span>)<\/span> {<\/span>\n        return<\/span> fetchAnotherData<\/span>(<\/span>data<\/span>)<\/span>\n        .<\/span>then<\/span>(<\/span>moreData<\/span> =><\/span> {<\/span>\n          return<\/span> moreData<\/span>\n        }<\/span>)<\/span>\n    }<\/span> else<\/span> {<\/span>\n      return<\/span> data<\/span>\n    }<\/span>\n  }<\/span>)<\/span>;<\/span>\n}<\/span>\n\n\/\/ better<\/span>\nasync<\/span> function<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  const<\/span> data<\/span> =<\/span> await<\/span> fetchData<\/span>(<\/span>)<\/span>\n  if<\/span> (<\/span>data<\/span>.<\/span>moreData<\/span>)<\/span> {<\/span>\n    const<\/span> moreData<\/span> =<\/span> await<\/span> fetchAnotherData<\/span>(<\/span>data<\/span>)<\/span>;<\/span>\n    return<\/span> moreData<\/span>\n  }<\/span> else<\/span> {<\/span>\n    return<\/span> data<\/span>\n  }<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 8-3<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  return<\/span> (<\/span>\n    fetchData<\/span>(<\/span>)<\/span>\n    .<\/span>then<\/span>(<\/span>value1<\/span> =><\/span> {<\/span>\n      return<\/span> fetchMoreData<\/span>(<\/span>value1<\/span>)<\/span>\n    }<\/span>)<\/span>\n    .<\/span>then<\/span>(<\/span>value2<\/span> =><\/span> {<\/span>\n      return<\/span> fetchMoreData2<\/span>(<\/span>value2<\/span>)<\/span>\n    }<\/span>)<\/span>\n  )<\/span>\n}<\/span>\n\n\/\/ better<\/span>\nasync<\/span> function<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  const<\/span> value1<\/span> =<\/span> await<\/span> fetchData<\/span>(<\/span>)<\/span>\n  const<\/span> value2<\/span> =<\/span> await<\/span> fetchMoreData<\/span>(<\/span>value1<\/span>)<\/span>\n  return<\/span> fetchMoreData2<\/span>(<\/span>value2<\/span>)<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
      2. \u9519\u8bef\u5904\u7406<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 8-4<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  try<\/span> {<\/span>\n    fetchData<\/span>(<\/span>)<\/span>\n      .<\/span>then<\/span>(<\/span>result<\/span> =><\/span> {<\/span>\n        const<\/span> data<\/span> =<\/span> JSON<\/span>.<\/span>parse<\/span>(<\/span>result<\/span>)<\/span>\n      }<\/span>)<\/span>\n      .<\/span>catch<\/span>(<\/span>(<\/span>err<\/span>)<\/span> =><\/span> {<\/span>\n        console<\/span>.<\/span>log<\/span>(<\/span>err<\/span>)<\/span>\n      }<\/span>)<\/span>\n  }<\/span> catch<\/span> (<\/span>err<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>err<\/span>)<\/span>\n  }<\/span>\n}<\/span>\n\n\/\/ better<\/span>\nasync<\/span> function<\/span> fetch<\/span>(<\/span>)<\/span> {<\/span>\n  try<\/span> {<\/span>\n    const<\/span> data<\/span> =<\/span> JSON<\/span>.<\/span>parse<\/span>(<\/span>await<\/span> fetchData<\/span>(<\/span>)<\/span>)<\/span>\n  }<\/span> catch<\/span> (<\/span>err<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>err<\/span>)<\/span>\n  }<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
      3. “async \u5730\u72f1”<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 8-5<\/span>\n\n\/\/ bad<\/span>\n(<\/span>async<\/span> (<\/span>)<\/span> =><\/span> {<\/span>\n  const<\/span> getList<\/span> =<\/span> await<\/span> getList<\/span>(<\/span>)<\/span>;<\/span>\n  const<\/span> getAnotherList<\/span> =<\/span> await<\/span> getAnotherList<\/span>(<\/span>)<\/span>;<\/span>\n}<\/span>)<\/span>(<\/span>)<\/span>;<\/span>\n\n\/\/ good<\/span>\n(<\/span>async<\/span> (<\/span>)<\/span> =><\/span> {<\/span>\n  const<\/span> listPromise<\/span> =<\/span> getList<\/span>(<\/span>)<\/span>;<\/span>\n  const<\/span> anotherListPromise<\/span> =<\/span> getAnotherList<\/span>(<\/span>)<\/span>;<\/span>\n  await<\/span> listPromise<\/span>;<\/span>\n  await<\/span> anotherListPromise<\/span>;<\/span>\n}<\/span>)<\/span>(<\/span>)<\/span>;<\/span>\n\n\/\/ good<\/span>\n(<\/span>async<\/span> (<\/span>)<\/span> =><\/span> {<\/span>\n  Promise<\/span>.<\/span>all<\/span>(<\/span>[<\/span>getList<\/span>(<\/span>)<\/span>,<\/span> getAnotherList<\/span>(<\/span>)<\/span>]<\/span>)<\/span>.<\/span>then<\/span>(<\/span>...)<\/span>;<\/span>\n}<\/span>)<\/span>(<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      9. Class<\/h2>\n
      \u6784\u9020\u51fd\u6570\u5c3d\u53ef\u80fd\u4f7f\u7528 Class \u7684\u5f62\u5f0f<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 9-1<\/span>\n\nclass<\/span> Foo<\/span> {<\/span>\n  static<\/span> bar<\/span> (<\/span>)<\/span> {<\/span>\n    this<\/span>.<\/span>baz<\/span>(<\/span>)<\/span>;<\/span>\n  }<\/span>\n  static<\/span> baz<\/span> (<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>'hello'<\/span>)<\/span>;<\/span>\n  }<\/span>\n  baz<\/span> (<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>'world'<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\nFoo<\/span>.<\/span>bar<\/span>(<\/span>)<\/span>;<\/span> \/\/ hello<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 9-2<\/span>\n\nclass<\/span> Shape<\/span> {<\/span>\n  constructor<\/span>(<\/span>width<\/span>,<\/span> height<\/span>)<\/span> {<\/span>\n    this<\/span>.<\/span>_width<\/span> =<\/span> width<\/span>;<\/span>\n    this<\/span>.<\/span>_height<\/span> =<\/span> height<\/span>;<\/span>\n  }<\/span>\n  get<\/span> area<\/span>(<\/span>)<\/span> {<\/span>\n    return<\/span> this<\/span>.<\/span>_width<\/span> *<\/span> this<\/span>.<\/span>_height<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\nconst<\/span> square<\/span> =<\/span> new<\/span> Shape<\/span>(<\/span>10<\/span>,<\/span> 10<\/span>)<\/span>;<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>square<\/span>.<\/span>area<\/span>)<\/span>;<\/span>    \/\/ 100<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>square<\/span>.<\/span>_width<\/span>)<\/span>;<\/span>  \/\/ 10<\/span><\/pre>\n<\/div>\n
      10.Decorator<\/h2>\n
      1. log<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 10-1<\/span>\n\nclass<\/span> Math<\/span> {<\/span>\n  @log<\/span>\n  add<\/span>(<\/span>a<\/span>,<\/span> b<\/span>)<\/span> {<\/span>\n    return<\/span> a<\/span> +<\/span> b<\/span>;<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
      log \u7684\u5b9e\u73b0\u53ef\u4ee5\u53c2\u8003 \u300aES6 \u7cfb\u5217\u4e4b\u6211\u4eec\u6765\u804a\u804a\u88c5\u9970\u5668\u300b<\/a><\/p>\n
      2. autobind<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 10-2<\/span>\n\nclass<\/span> Toggle<\/span> extends<\/span> React<\/span>.<\/span>Component<\/span> {<\/span>\n\n  @autobind<\/span>\n  handleClick<\/span>(<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>this<\/span>)<\/span>\n  }<\/span>\n\n  render<\/span>(<\/span>)<\/span> {<\/span>\n    return<\/span> (<\/span>\n      <<\/span>button<\/span> onClick<\/span>=<\/span>{<\/span>this<\/span>.<\/span>handleClick<\/span>}<\/span>><\/span>\n        button\n      <<\/span>\/<\/span>button<\/span>><\/span>\n    )<\/span>;<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
      autobind \u7684\u5b9e\u73b0\u53ef\u4ee5\u53c2\u8003 \u300aES6 \u7cfb\u5217\u4e4b\u6211\u4eec\u6765\u804a\u804a\u88c5\u9970\u5668\u300b<\/a><\/p>\n
      3. debounce<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 10-3<\/span>\n\nclass<\/span> Toggle<\/span> extends<\/span> React<\/span>.<\/span>Component<\/span> {<\/span>\n\n  @debounce<\/span>(<\/span>500<\/span>,<\/span> true<\/span>)<\/span>\n  handleClick<\/span>(<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>'toggle'<\/span>)<\/span>\n  }<\/span>\n\n  render<\/span>(<\/span>)<\/span> {<\/span>\n    return<\/span> (<\/span>\n      <<\/span>button<\/span> onClick<\/span>=<\/span>{<\/span>this<\/span>.<\/span>handleClick<\/span>}<\/span>><\/span>\n        button\n      <<\/span>\/<\/span>button<\/span>><\/span>\n    )<\/span>;<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
      debounce \u7684\u5b9e\u73b0\u53ef\u4ee5\u53c2\u8003 \u300aES6 \u7cfb\u5217\u4e4b\u6211\u4eec\u6765\u804a\u804a\u88c5\u9970\u5668\u300b<\/a><\/p>\n
      4. React \u4e0e Redux<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 10-4<\/span>\n\n\/\/ good<\/span>\nclass<\/span> MyReactComponent<\/span> extends<\/span> React<\/span>.<\/span>Component<\/span> {<\/span>}<\/span>\n\nexport<\/span> default<\/span> connect<\/span>(<\/span>mapStateToProps<\/span>,<\/span> mapDispatchToProps<\/span>)<\/span>(<\/span>MyReactComponent<\/span>)<\/span>;<\/span>\n\n\/\/ better<\/span>\n@connect<\/span>(<\/span>mapStateToProps<\/span>,<\/span> mapDispatchToProps<\/span>)<\/span>\nexport<\/span> default<\/span> class<\/span> MyReactComponent<\/span> extends<\/span> React<\/span>.<\/span>Component<\/span> {<\/span>}<\/span>;<\/span><\/pre>\n<\/div>\n
      11. \u51fd\u6570<\/h2>\n
      1. \u9ed8\u8ba4\u503c<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 11-1<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> test<\/span>(<\/span>quantity<\/span>)<\/span> {<\/span>\n  const<\/span> q<\/span> =<\/span> quantity<\/span> ||<\/span> 1<\/span>;<\/span>\n}<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> test<\/span>(<\/span>quantity<\/span> =<\/span> 1<\/span>)<\/span> {<\/span>\n  ...\n}<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 11-2<\/span>\n\ndoSomething<\/span>(<\/span>{<\/span> foo<\/span>: 'Hello'<\/span>,<\/span> bar<\/span>: 'Hey!'<\/span>,<\/span> baz<\/span>: 42<\/span> }<\/span>)<\/span>;<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> doSomething<\/span>(<\/span>config<\/span>)<\/span> {<\/span>\n  const<\/span> foo<\/span> =<\/span> config<\/span>.<\/span>foo<\/span> !==<\/span> undefined<\/span> ? config<\/span>.<\/span>foo<\/span> : 'Hi'<\/span>;<\/span>\n  const<\/span> bar<\/span> =<\/span> config<\/span>.<\/span>bar<\/span> !==<\/span> undefined<\/span> ? config<\/span>.<\/span>bar<\/span> : 'Yo!'<\/span>;<\/span>\n  const<\/span> baz<\/span> =<\/span> config<\/span>.<\/span>baz<\/span> !==<\/span> undefined<\/span> ? config<\/span>.<\/span>baz<\/span> : 13<\/span>;<\/span>\n}<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> doSomething<\/span>(<\/span>{<\/span> foo =<\/span> 'Hi'<\/span>,<\/span> bar =<\/span> 'Yo!'<\/span>,<\/span> baz =<\/span> 13<\/span> }<\/span>)<\/span> {<\/span>\n  ...\n}<\/span>\n\n\/\/ better<\/span>\nfunction<\/span> doSomething<\/span>(<\/span>{<\/span> foo =<\/span> 'Hi'<\/span>,<\/span> bar =<\/span> 'Yo!'<\/span>,<\/span> baz =<\/span> 13<\/span> }<\/span> =<\/span> {<\/span>}<\/span>)<\/span> {<\/span>\n  ...\n}<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 11-3<\/span>\n\n\/\/ bad<\/span>\nconst<\/span> Button<\/span> =<\/span> (<\/span>{<\/span>className}<\/span>)<\/span> =><\/span> {<\/span>\n\tconst<\/span> classname<\/span> =<\/span> className<\/span> ||<\/span> 'default-size'<\/span>;<\/span>\n\treturn<\/span> <<\/span>span<\/span> className<\/span>=<\/span>{<\/span>classname<\/span>}<\/span>><\/span><<\/span>\/<\/span>span<\/span>><\/span>\n}<\/span>;<\/span>\n\n\/\/ good<\/span>\nconst<\/span> Button<\/span> =<\/span> (<\/span>{<\/span>className =<\/span> 'default-size'<\/span>}<\/span>)<\/span> =><\/span> (<\/span>\n\t<<\/span>span<\/span> className<\/span>=<\/span>{<\/span>classname<\/span>}<\/span>><\/span><<\/span>\/<\/span>span<\/span>><\/span>\n)<\/span>;<\/span>\n\n\/\/ better<\/span>\nconst<\/span> Button<\/span> =<\/span> (<\/span>{<\/span>className}<\/span>)<\/span> =><\/span>\n\t<<\/span>span<\/span> className<\/span>=<\/span>{<\/span>className<\/span>}<\/span>><\/span><<\/span>\/<\/span>span<\/span>><\/span>\n}<\/span>\n\nButton<\/span>.<\/span>defaultProps<\/span> =<\/span> {<\/span>\n\tclassName<\/span>: 'default-size'<\/span>\n}<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 11-4<\/span>\n\nconst<\/span> required<\/span> =<\/span> (<\/span>)<\/span> =><\/span> {<\/span>throw<\/span> new<\/span> Error<\/span>(<\/span>'Missing parameter'<\/span>)<\/span>}<\/span>;<\/span>\n\nconst<\/span> add<\/span> =<\/span> (<\/span>a<\/span> =<\/span> required<\/span>(<\/span>)<\/span>,<\/span> b<\/span> =<\/span> required<\/span>(<\/span>)<\/span>)<\/span> =><\/span> a<\/span> +<\/span> b<\/span>;<\/span>\n\nadd<\/span>(<\/span>1<\/span>,<\/span> 2<\/span>)<\/span> \/\/ 3<\/span>\nadd<\/span>(<\/span>1<\/span>)<\/span>;<\/span> \/\/ Error: Missing parameter.<\/span><\/pre>\n<\/div>\n
      12. \u62d3\u5c55\u8fd0\u7b97\u7b26<\/h2>\n
      1. arguments \u8f6c\u6570\u7ec4<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 12-1<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> sortNumbers<\/span>(<\/span>)<\/span> {<\/span>\n  return<\/span> Array<\/span>.<\/span>prototype<\/span>.<\/span>slice<\/span>.<\/span>call<\/span>(<\/span>arguments<\/span>)<\/span>.<\/span>sort<\/span>(<\/span>)<\/span>;<\/span>\n}<\/span>\n\n\/\/ good<\/span>\nconst<\/span> sortNumbers<\/span> =<\/span> (<\/span>...numbers<\/span>)<\/span> =><\/span> numbers<\/span>.<\/span>sort<\/span>(<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      2. \u8c03\u7528\u53c2\u6570<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 12-2<\/span>\n\n\/\/ bad<\/span>\nMath<\/span>.<\/span>max<\/span>.<\/span>apply<\/span>(<\/span>null<\/span>,<\/span> [<\/span>14<\/span>,<\/span> 3<\/span>,<\/span> 77<\/span>]<\/span>)<\/span>\n\n\/\/ good<\/span>\nMath<\/span>.<\/span>max<\/span>(<\/span>...[<\/span>14<\/span>,<\/span> 3<\/span>,<\/span> 77<\/span>]<\/span>)<\/span>\n\/\/ \u7b49\u540c\u4e8e<\/span>\nMath<\/span>.<\/span>max<\/span>(<\/span>14<\/span>,<\/span> 3<\/span>,<\/span> 77<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      3. \u6784\u5efa\u5bf9\u8c61<\/h3>\n
      \u5254\u9664\u90e8\u5206\u5c5e\u6027\uff0c\u5c06\u5269\u4e0b\u7684\u5c5e\u6027\u6784\u5efa\u4e00\u4e2a\u65b0\u7684\u5bf9\u8c61<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 12-3<\/span>\nlet<\/span> [<\/span>a<\/span>,<\/span> b<\/span>,<\/span> ...arr<\/span>]<\/span> =<\/span> [<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> 4<\/span>,<\/span> 5<\/span>]<\/span>;<\/span>\n\nconst<\/span> {<\/span> a,<\/span> b,<\/span> ...others<\/span> }<\/span> =<\/span> {<\/span> a<\/span>: 1<\/span>,<\/span> b<\/span>: 2<\/span>,<\/span> c<\/span>: 3<\/span>,<\/span> d<\/span>: 4<\/span>,<\/span> e<\/span>: 5<\/span> }<\/span>;<\/span><\/pre>\n<\/div>\n
      \u6709\u6761\u4ef6\u7684\u6784\u5efa\u5bf9\u8c61<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 12-4<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> pick<\/span>(<\/span>data<\/span>)<\/span> {<\/span>\n  const<\/span> {<\/span> id,<\/span> name,<\/span> age}<\/span> =<\/span> data<\/span>\n\n  const<\/span> res<\/span> =<\/span> {<\/span> guid<\/span>: id<\/span> }<\/span>\n\n  if<\/span> (<\/span>name<\/span>)<\/span> {<\/span>\n    res<\/span>.<\/span>name<\/span> =<\/span> name<\/span>\n  }<\/span>\n  else<\/span> if<\/span> (<\/span>age<\/span>)<\/span> {<\/span>\n    res<\/span>.<\/span>age<\/span> =<\/span> age<\/span>\n  }<\/span>\n\n  return<\/span> res<\/span>\n}<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> pick<\/span>(<\/span>{<\/span>id,<\/span> name,<\/span> age}<\/span>)<\/span> {<\/span>\n  return<\/span> {<\/span>\n    guid<\/span>: id<\/span>,<\/span>\n    ...(<\/span>name<\/span> &&<\/span> {<\/span>name}<\/span>)<\/span>,<\/span>\n    ...(<\/span>age<\/span> &&<\/span> {<\/span>age}<\/span>)<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
      \u5408\u5e76\u5bf9\u8c61<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 12-5<\/span>\n\nlet<\/span> obj1<\/span> =<\/span> {<\/span> a<\/span>: 1<\/span>,<\/span> b<\/span>: 2<\/span>,<\/span>c<\/span>: 3<\/span> }<\/span>\nlet<\/span> obj2<\/span> =<\/span> {<\/span> b<\/span>: 4<\/span>,<\/span> c<\/span>: 5<\/span>,<\/span> d<\/span>: 6<\/span>}<\/span>\nlet<\/span> merged<\/span> =<\/span> {<\/span>...obj1<\/span>,<\/span> ...obj2<\/span>}<\/span>;<\/span><\/pre>\n<\/div>\n
      4. React<\/h3>\n
      \u5c06\u5bf9\u8c61\u5168\u90e8\u4f20\u5165\u7ec4\u4ef6<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 12-6<\/span>\n\nconst<\/span> parmas<\/span> =<\/span>  {<\/span>value1<\/span>: 1<\/span>,<\/span> value2<\/span>: 2<\/span>,<\/span> value3<\/span>: 3<\/span>}<\/span>\n\n<<\/span>Test<\/span> {<\/span>...parmas<\/span>}<\/span> \/<\/span>><\/span><\/pre>\n<\/div>\n
      13. \u53cc\u5192\u53f7\u8fd0\u7b97\u7b26<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 13-1<\/span>\n\nfoo::bar<\/span>;<\/span>\n\/\/ \u7b49\u540c\u4e8e<\/span>\nbar<\/span>.<\/span>bind<\/span>(<\/span>foo<\/span>)<\/span>;<\/span>\n\nfoo::bar<\/span>(<\/span>...arguments<\/span>)<\/span>;<\/span>\n\/\/ \u7b49\u540c\u4e8e<\/span>\nbar<\/span>.<\/span>apply<\/span>(<\/span>foo<\/span>,<\/span> arguments<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      \u5982\u679c\u53cc\u5192\u53f7\u5de6\u8fb9\u4e3a\u7a7a\uff0c\u53f3\u8fb9\u662f\u4e00\u4e2a\u5bf9\u8c61\u7684\u65b9\u6cd5\uff0c\u5219\u7b49\u4e8e\u5c06\u8be5\u65b9\u6cd5\u7ed1\u5b9a\u5728\u8be5\u5bf9\u8c61\u4e0a\u9762\u3002<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 13-2<\/span>\n\nvar<\/span> method<\/span> =<\/span> obj<\/span>::obj<\/span>.<\/span>foo<\/span>;<\/span>\n\/\/ \u7b49\u540c\u4e8e<\/span>\nvar<\/span> method<\/span> =<\/span> ::obj<\/span>.<\/span>foo<\/span>;<\/span>\n\nlet<\/span> log<\/span> =<\/span> ::console<\/span>.<\/span>log<\/span>;<\/span>\n\/\/ \u7b49\u540c\u4e8e<\/span>\nvar<\/span> log<\/span> =<\/span> console<\/span>.<\/span>log<\/span>.<\/span>bind<\/span>(<\/span>console<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      14. \u89e3\u6784\u8d4b\u503c<\/h2>\n
      1. \u5bf9\u8c61\u7684\u57fa\u672c\u89e3\u6784<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-1<\/span>\n\ncomponentWillReceiveProps<\/span>(<\/span>newProps<\/span>)<\/span><\/span> {<\/span>\n\tthis<\/span>.<\/span>setState<\/span>(<\/span>{<\/span>\n\t\tactive<\/span>: newProps<\/span>.<\/span>active<\/span>\n\t}<\/span>)<\/span>\n}<\/span>\n\ncomponentWillReceiveProps<\/span>(<\/span>{<\/span>active}<\/span>)<\/span><\/span> {<\/span>\n\tthis<\/span>.<\/span>setState<\/span>(<\/span>{<\/span>active}<\/span>)<\/span>\n}<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-2<\/span>\n\n\/\/ bad<\/span>\nhandleEvent<\/span> =<\/span> (<\/span>)<\/span> =><\/span> {<\/span>\n  this<\/span>.<\/span>setState<\/span>(<\/span>{<\/span>\n    data<\/span>: this<\/span>.<\/span>state<\/span>.<\/span>data<\/span>.<\/span>set<\/span>(<\/span>\"key\"<\/span>,<\/span> \"value\"<\/span>)<\/span>\n  }<\/span>)<\/span>\n}<\/span>;<\/span>\n\n\/\/ good<\/span>\nhandleEvent<\/span> =<\/span> (<\/span>)<\/span> =><\/span> {<\/span>\n  this<\/span>.<\/span>setState<\/span>(<\/span>(<\/span>{<\/span>data}<\/span>)<\/span> =><\/span> (<\/span>{<\/span>\n    data<\/span>: data<\/span>.<\/span>set<\/span>(<\/span>\"key\"<\/span>,<\/span> \"value\"<\/span>)<\/span>\n  }<\/span>)<\/span>)<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-3<\/span>\n\nPromise<\/span>.<\/span>all<\/span>(<\/span>[<\/span>Promise<\/span>.<\/span>resolve<\/span>(<\/span>1<\/span>)<\/span>,<\/span> Promise<\/span>.<\/span>resolve<\/span>(<\/span>2<\/span>)<\/span>]<\/span>)<\/span>\n.<\/span>then<\/span>(<\/span>(<\/span>[<\/span>x<\/span>,<\/span> y<\/span>]<\/span>)<\/span> =><\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>x<\/span>,<\/span> y<\/span>)<\/span>;<\/span>\n}<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      2. \u5bf9\u8c61\u6df1\u5ea6\u89e3\u6784<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-4<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> test<\/span>(<\/span>fruit<\/span>)<\/span> {<\/span>\n  if<\/span> (<\/span>fruit<\/span> &&<\/span> fruit<\/span>.<\/span>name<\/span>)<\/span>  {<\/span>\n    console<\/span>.<\/span>log<\/span> (<\/span>fruit<\/span>.<\/span>name<\/span>)<\/span>;<\/span>\n  }<\/span> else<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>'unknown'<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> test<\/span>(<\/span>{<\/span>name}<\/span> =<\/span> {<\/span>}<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span> (<\/span>name<\/span> ||<\/span> 'unknown'<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-5<\/span>\n\nlet<\/span> obj<\/span> =<\/span> {<\/span>\n    a<\/span>: {<\/span>\n      b<\/span>: {<\/span>\n        c<\/span>: 1<\/span>\n      }<\/span>\n    }<\/span>\n}<\/span>;<\/span>\n\nconst<\/span> {<\/span>a<\/span>: {<\/span>b<\/span>: {<\/span>c =<\/span> ''<\/span>}<\/span> =<\/span> ''} = '<\/span>'} = obj;<\/pre>\n<\/div>\n
      3. \u6570\u7ec4\u89e3\u6784<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-6<\/span>\n\n\/\/ bad<\/span>\nconst<\/span> splitLocale<\/span> =<\/span> locale<\/span>.<\/span>split<\/span>(<\/span>\"-\"<\/span>)<\/span>;<\/span>\nconst<\/span> language<\/span> =<\/span> splitLocale<\/span>[<\/span>0<\/span>]<\/span>;<\/span>\nconst<\/span> country<\/span> =<\/span> splitLocale<\/span>[<\/span>1<\/span>]<\/span>;<\/span>\n\n\/\/ good<\/span>\nconst<\/span> [<\/span>language<\/span>,<\/span> country<\/span>]<\/span> =<\/span> locale<\/span>.<\/span>split<\/span>(<\/span>'-'<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      4. \u53d8\u91cf\u91cd\u547d\u540d<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-8<\/span>\n\nlet<\/span> {<\/span> foo<\/span>: baz<\/span> }<\/span> =<\/span> {<\/span> foo<\/span>: 'aaa'<\/span>,<\/span> bar<\/span>: 'bbb'<\/span> }<\/span>;<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>baz<\/span>)<\/span>;<\/span> \/\/ \"aaa\"<\/span><\/pre>\n<\/div>\n
      5. \u4ec5\u83b7\u53d6\u90e8\u5206\u5c5e\u6027<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 14-9<\/span>\n\nfunction<\/span> test<\/span>(<\/span>input<\/span>)<\/span> {<\/span>\n  return<\/span> [<\/span>left<\/span>,<\/span> right<\/span>,<\/span> top<\/span>,<\/span> bottom<\/span>]<\/span>;<\/span>\n}<\/span>\nconst<\/span> [<\/span>left<\/span>,<\/span> __<\/span>,<\/span> top<\/span>]<\/span> =<\/span> test<\/span>(<\/span>input<\/span>)<\/span>;<\/span>\n\nfunction<\/span> test<\/span>(<\/span>input<\/span>)<\/span> {<\/span>\n  return<\/span> {<\/span> left,<\/span> right,<\/span> top,<\/span> bottom }<\/span>;<\/span>\n}<\/span>\nconst<\/span> {<\/span> left,<\/span> right }<\/span> =<\/span> test<\/span>(<\/span>input<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      15. \u589e\u5f3a\u7684\u5bf9\u8c61\u5b57\u9762\u91cf<\/h2>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 15-1<\/span>\n\n\/\/ bad<\/span>\nconst<\/span> something<\/span> =<\/span> 'y'<\/span>\nconst<\/span> x<\/span> =<\/span> {<\/span>\n  something<\/span>: something<\/span>\n}<\/span>\n\n\/\/ good<\/span>\nconst<\/span> something<\/span> =<\/span> 'y'<\/span>\nconst<\/span> x<\/span> =<\/span> {<\/span>\n  something\n}<\/span>;<\/span><\/pre>\n<\/div>\n
      \u52a8\u6001\u5c5e\u6027<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 15-2<\/span>\n\nconst<\/span> x<\/span> =<\/span> {<\/span>\n  [<\/span>'a'<\/span> +<\/span> '_'<\/span> +<\/span> 'b'<\/span>]<\/span>: 'z'<\/span>\n}<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>x<\/span>.<\/span>a_b<\/span>)<\/span>;<\/span> \/\/ z<\/span><\/pre>\n<\/div>\n
      16. \u6570\u7ec4\u7684\u62d3\u5c55\u65b9\u6cd5<\/h2>\n
      1. keys<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 16-1<\/span>\n\nvar<\/span> arr<\/span> =<\/span> [<\/span>\"a\"<\/span>,<\/span> ,<\/span> \"c\"<\/span>]<\/span>;<\/span>\n\nvar<\/span> sparseKeys<\/span> =<\/span> Object<\/span>.<\/span>keys<\/span>(<\/span>arr<\/span>)<\/span>;<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>sparseKeys<\/span>)<\/span>;<\/span> \/\/ ['0', '2']<\/span>\n\nvar<\/span> denseKeys<\/span> =<\/span> [<\/span>...arr<\/span>.<\/span>keys<\/span>(<\/span>)<\/span>]<\/span>;<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>denseKeys<\/span>)<\/span>;<\/span>  \/\/ [0, 1, 2]<\/span><\/pre>\n<\/div>\n
      2. entries<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 16-2<\/span>\n\nvar<\/span> arr<\/span> =<\/span> [<\/span>\"a\"<\/span>,<\/span> \"b\"<\/span>,<\/span> \"c\"<\/span>]<\/span>;<\/span>\nvar<\/span> iterator<\/span> =<\/span> arr<\/span>.<\/span>entries<\/span>(<\/span>)<\/span>;<\/span>\n\nfor<\/span> (<\/span>let<\/span> e<\/span> of<\/span> iterator<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>e<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
      3. values<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 16-3<\/span>\n\nlet<\/span> arr<\/span> =<\/span> [<\/span>'w'<\/span>,<\/span> 'y'<\/span>,<\/span> 'k'<\/span>,<\/span> 'o'<\/span>,<\/span> 'p'<\/span>]<\/span>;<\/span>\nlet<\/span> eArr<\/span> =<\/span> arr<\/span>.<\/span>values<\/span>(<\/span>)<\/span>;<\/span>\n\nfor<\/span> (<\/span>let<\/span> letter<\/span> of<\/span> eArr<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>letter<\/span>)<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
      4. includes<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 16-4<\/span>\n\n\/\/ bad<\/span>\nfunction<\/span> test<\/span>(<\/span>fruit<\/span>)<\/span> {<\/span>\n  if<\/span> (<\/span>fruit<\/span> ==<\/span> 'apple'<\/span> ||<\/span> fruit<\/span> ==<\/span> 'strawberry'<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>'red'<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\n\/\/ good<\/span>\nfunction<\/span> test<\/span>(<\/span>fruit<\/span>)<\/span> {<\/span>\n  const<\/span> redFruits<\/span> =<\/span> [<\/span>'apple'<\/span>,<\/span> 'strawberry'<\/span>,<\/span> 'cherry'<\/span>,<\/span> 'cranberries'<\/span>]<\/span>;<\/span>\n  if<\/span> (<\/span>redFruits<\/span>.<\/span>includes<\/span>(<\/span>fruit<\/span>)<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>'red'<\/span>)<\/span>;<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/div>\n
      5. find<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 16-5<\/span>\n\nvar<\/span> inventory<\/span> =<\/span> [<\/span>\n    {<\/span>name<\/span>: 'apples'<\/span>,<\/span> quantity<\/span>: 2<\/span>}<\/span>,<\/span>\n    {<\/span>name<\/span>: 'bananas'<\/span>,<\/span> quantity<\/span>: 0<\/span>}<\/span>,<\/span>\n    {<\/span>name<\/span>: 'cherries'<\/span>,<\/span> quantity<\/span>: 5<\/span>}<\/span>\n]<\/span>;<\/span>\n\nfunction<\/span> findCherries<\/span>(<\/span>fruit<\/span>)<\/span> {<\/span>\n    return<\/span> fruit<\/span>.<\/span>name<\/span> ===<\/span> 'cherries'<\/span>;<\/span>\n}<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>inventory<\/span>.<\/span>find<\/span>(<\/span>findCherries<\/span>)<\/span>)<\/span>;<\/span> \/\/ { name: 'cherries', quantity: 5 }<\/span><\/pre>\n<\/div>\n
      6. findIndex<\/h3>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 16-6<\/span>\n\nfunction<\/span> isPrime<\/span>(<\/span>element<\/span>,<\/span> index<\/span>,<\/span> array<\/span>)<\/span> {<\/span>\n  var<\/span> start<\/span> =<\/span> 2<\/span>;<\/span>\n  while<\/span> (<\/span>start<\/span> <=<\/span> Math<\/span>.<\/span>sqrt<\/span>(<\/span>element<\/span>)<\/span>)<\/span> {<\/span>\n    if<\/span> (<\/span>element<\/span> %<\/span> start<\/span>++<\/span> <<\/span> 1<\/span>)<\/span> {<\/span>\n      return<\/span> false<\/span>;<\/span>\n    }<\/span>\n  }<\/span>\n  return<\/span> element<\/span> ><\/span> 1<\/span>;<\/span>\n}<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>[<\/span>4<\/span>,<\/span> 6<\/span>,<\/span> 8<\/span>,<\/span> 12<\/span>]<\/span>.<\/span>findIndex<\/span>(<\/span>isPrime<\/span>)<\/span>)<\/span>;<\/span> \/\/ -1, not found<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>[<\/span>4<\/span>,<\/span> 6<\/span>,<\/span> 7<\/span>,<\/span> 12<\/span>]<\/span>.<\/span>findIndex<\/span>(<\/span>isPrime<\/span>)<\/span>)<\/span>;<\/span> \/\/ 2<\/span><\/pre>\n<\/div>\n
      \u66f4\u591a\u7684\u5c31\u4e0d\u5217\u4e3e\u4e86\u3002<\/p>\n
      17. optional-chaining<\/a><\/h2>\n
      \u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 17-1<\/span>\n\nconst<\/span> obj<\/span> =<\/span> {<\/span>\n  foo<\/span>: {<\/span>\n    bar<\/span>: {<\/span>\n      baz<\/span>: 42<\/span>,<\/span>\n    }<\/span>,<\/span>\n  }<\/span>,<\/span>\n}<\/span>;<\/span>\n\nconst<\/span> baz<\/span> =<\/span> obj<\/span>?.<\/span>foo<\/span>?.<\/span>bar<\/span>?.<\/span>baz<\/span>;<\/span> \/\/ 42<\/span><\/pre>\n<\/div>\n
      \u540c\u6837\u652f\u6301\u51fd\u6570\uff1a<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 17-2<\/span>\n\nfunction<\/span> test<\/span>(<\/span>)<\/span> {<\/span>\n  return<\/span> 42<\/span>;<\/span>\n}<\/span>\ntest<\/span>?.<\/span>(<\/span>)<\/span>;<\/span> \/\/ 42<\/span>\n\nexists<\/span>?.<\/span>(<\/span>)<\/span>;<\/span> \/\/ undefined<\/span><\/pre>\n<\/div>\n
      \u9700\u8981\u6dfb\u52a0 @babel\/plugin-proposal-optional-chaining<\/a> \u63d2\u4ef6\u652f\u6301<\/p>\n
      18. logical-assignment-operators<\/h2>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 18-1<\/span>\n\na<\/span> ||=<\/span> b<\/span>;<\/span>\n\nobj<\/span>.<\/span>a<\/span>.<\/span>b<\/span> ||=<\/span> c<\/span>;<\/span>\n\na<\/span> &&=<\/span> b<\/span>;<\/span>\n\nobj<\/span>.<\/span>a<\/span>.<\/span>b<\/span> &&=<\/span> c<\/span>;<\/span><\/pre>\n<\/div>\n
      Babel \u7f16\u8bd1\u4e3a\uff1a<\/p>\n
      <\/p>\n
      var<\/span> _obj$a<\/span>,<\/span> _obj$a2<\/span>;<\/span>\n\na<\/span> ||<\/span> (<\/span>a<\/span> =<\/span> b<\/span>)<\/span>;<\/span>\n\n(<\/span>_obj$a<\/span> =<\/span> obj<\/span>.<\/span>a<\/span>)<\/span>.<\/span>b<\/span> ||<\/span> (<\/span>_obj$a<\/span>.<\/span>b<\/span> =<\/span> c<\/span>)<\/span>;<\/span>\n\na<\/span> &&<\/span> (<\/span>a<\/span> =<\/span> b<\/span>)<\/span>;<\/span>\n\n(<\/span>_obj$a2<\/span> =<\/span> obj<\/span>.<\/span>a<\/span>)<\/span>.<\/span>b<\/span> &&<\/span> (<\/span>_obj$a2<\/span>.<\/span>b<\/span> =<\/span> c<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
      \u51fa\u73b0\u7684\u539f\u56e0\uff1a<\/p>\n
      <\/p>\n
      \/\/ \u4f8b\u5b50 18-2<\/span>\n\nfunction<\/span> example<\/span>(<\/span>a<\/span> =<\/span> b<\/span>)<\/span> {<\/span>\n  \/\/ a \u5fc5\u987b\u662f undefined<\/span>\n  if<\/span> (<\/span>!<\/span>a<\/span>)<\/span> {<\/span>\n    a<\/span> =<\/span> b<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\nfunction<\/span> numeric<\/span>(<\/span>a<\/span> =<\/span> b<\/span>)<\/span> {<\/span>\n  \/\/ a \u5fc5\u987b\u662f null \u6216\u8005 undefined<\/span>\n  if<\/span> (<\/span>a<\/span> ==<\/span> null<\/span>)<\/span> {<\/span>\n    a<\/span> =<\/span> b<\/span>;<\/span>\n  }<\/span>\n}<\/span>\n\n\/\/ a \u53ef\u4ee5\u662f\u4efb\u4f55 falsy \u7684\u503c<\/span>\nfunction<\/span> example<\/span>(<\/span>a<\/span> =<\/span> b<\/span>)<\/span> {<\/span>\n  \/\/ \u53ef\u4ee5\uff0c\u4f46\u662f\u4e00\u5b9a\u4f1a\u89e6\u53d1 setter<\/span>\n  a<\/span> =<\/span> a<\/span> ||<\/span> b<\/span>;<\/span>\n\n  \/\/ \u4e0d\u4f1a\u89e6\u53d1 setter\uff0c\u4f46\u53ef\u80fd\u4f1a\u5bfc\u81f4 lint error<\/span>\n  a<\/span> ||<\/span> (<\/span>a<\/span> =<\/span> b<\/span>)<\/span>;<\/span>\n\n  \/\/ \u5c31\u6709\u4eba\u63d0\u51fa\u4e86\u8fd9\u79cd\u5199\u6cd5\uff1a<\/span>\n  a<\/span> ||=<\/span> b<\/span>;<\/span>\n}<\/span><\/pre>\n<\/div>\n
      \u9700\u8981 @babel\/plugin-proposal-logical-assignment-operators<\/a> \u63d2\u4ef6\u652f\u6301<\/p>\n
      19. nullish-coalescing-operator<\/h2>\n
      <\/p>\n
      a<\/span> ??<\/span> b<\/span>\n\n\/\/ \u76f8\u5f53\u4e8e<\/span>\n\n(<\/span>a<\/span> !==<\/span> null<\/span> &&<\/span> a<\/span> !==<\/span> void<\/span> 0<\/span>)<\/span> ? a<\/span> : b<\/span><\/pre>\n<\/div>\n
      \u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n
      <\/p>\n
      var<\/span> foo<\/span> =<\/span> object<\/span>.<\/span>foo<\/span> ??<\/span> \"default\"<\/span>;<\/span>\n\n\/\/ \u76f8\u5f53\u4e8e<\/span>\n\nvar<\/span> foo<\/span> =<\/span> (<\/span>object<\/span>.<\/span>foo<\/span> !=<\/span> null<\/span>)<\/span> ? object<\/span>.<\/span>foo<\/span> : \"default\"<\/span>;<\/span><\/pre>\n<\/div>\n
      \u9700\u8981 @babel\/plugin-proposal-nullish-coalescing-operator<\/a> \u63d2\u4ef6\u652f\u6301<\/p>\n
      20. pipeline-operator<\/h2>\n
      <\/p>\n
      const<\/span> double<\/span> =<\/span> (<\/span>n<\/span>)<\/span> =><\/span> n<\/span> *<\/span> 2<\/span>;<\/span>\nconst<\/span> increment<\/span> =<\/span> (<\/span>n<\/span>)<\/span> =><\/span> n<\/span> +<\/span> 1<\/span>;<\/span>\n\n\/\/ \u6ca1\u6709\u7528\u7ba1\u9053\u64cd\u4f5c\u7b26<\/span>\ndouble<\/span>(<\/span>increment<\/span>(<\/span>double<\/span>(<\/span>5<\/span>)<\/span>)<\/span>)<\/span>;<\/span> \/\/ 22<\/span>\n\n\/\/ \u7528\u4e0a\u7ba1\u9053\u64cd\u4f5c\u7b26\u4e4b\u540e<\/span>\n5<\/span> |<\/span>><\/span> double<\/span> |<\/span>><\/span> increment<\/span> |<\/span>><\/span> double<\/span>;<\/span> \/\/ 22<\/span><\/pre>\n<\/div>\n
      \u5176\u4ed6<\/h2>\n
      \u65b0\u5f00\u4e86 \u77e5\u4e4e\u4e13\u680f<\/a>\uff0c\u5927\u5bb6\u53ef\u4ee5\u5728\u66f4\u591a\u7684\u5e73\u53f0\u4e0a\u770b\u5230\u6211\u7684\u6587\u7ae0\uff0c\u6b22\u8fce\u5173\u6ce8\u54e6~<\/p>\n
      \u53c2\u8003<\/h2>\n
        \n
      1. ES6 \u5b9e\u8df5\u89c4\u8303<\/a><\/li>\n
      2. babel 7 \u7b80\u5355\u5347\u7ea7\u6307\u5357<\/a><\/li>\n
      3. \u4e0d\u5f97\u4e0d\u77e5\u7684 ES6 \u5c0f\u6280\u5de7<\/a><\/li>\n
      4. \u6df1\u5165\u89e3\u6790 ES6\uff1aSymbol<\/a><\/li>\n
      5. \u4ec0\u4e48\u65f6\u5019\u4f60\u4e0d\u80fd\u4f7f\u7528\u7bad\u5934\u51fd\u6570\uff1f<\/a><\/li>\n
      6. \u4e00\u4e9b\u4f7f JavaScript \u66f4\u52a0\u7b80\u6d01\u7684\u5c0f\u6280\u5de7<\/a><\/li>\n
      7. \u51e0\u5206\u949f\u5185\u63d0\u5347\u6280\u80fd\u7684 8 \u4e2a JavaScript \u65b9\u6cd5<\/a><\/li>\n
      8. [\u8bd1] \u5982\u4f55\u4f7f\u7528 JavaScript ES6 \u6709\u6761\u4ef6\u5730\u6784\u9020\u5bf9\u8c61<\/a><\/li>\n
      9. 5 \u4e2a\u6280\u5de7\u8ba9\u4f60\u66f4\u597d\u7684\u7f16\u5199 JavaScript(ES6) \u4e2d\u6761\u4ef6\u8bed\u53e5<\/a><\/li>\n
      10. ES6 \u5e26\u6765\u7684\u91cd\u5927\u7279\u6027 \u2013 JavaScript \u5b8c\u5168\u624b\u518c\uff082018\u7248\uff09<\/a><\/li>\n<\/ol>\n
        ES6 \u7cfb\u5217<\/h2>\n
        ES6 \u7cfb\u5217\u76ee\u5f55\u5730\u5740\uff1ahttps:\/\/github.com\/mqyqingfeng\/Blog<\/a><\/p>\n
        ES6 \u7cfb\u5217\u9884\u8ba1\u5199\u4e8c\u5341\u7bc7\u5de6\u53f3\uff0c\u65e8\u5728\u52a0\u6df1 ES6 \u90e8\u5206\u77e5\u8bc6\u70b9\u7684\u7406\u89e3\uff0c\u91cd\u70b9\u8bb2\u89e3\u5757\u7ea7\u4f5c\u7528\u57df\u3001\u6807\u7b7e\u6a21\u677f\u3001\u7bad\u5934\u51fd\u6570\u3001Symbol\u3001Set\u3001Map \u4ee5\u53ca Promise \u7684\u6a21\u62df\u5b9e\u73b0\u3001\u6a21\u5757\u52a0\u8f7d\u65b9\u6848\u3001\u5f02\u6b65\u5904\u7406\u7b49\u5185\u5bb9\u3002<\/p>\n<\/td>\n
        \u6587\u7ae0\u8f6c\u8f7d\u81eahttps:\/\/github.com\/mqyqingfeng\/Blog\/issues\/111<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
        \u524d\u8a00 \u8fd9\u91cc\u7684 “ES6” \u6cdb\u6307 ES5 \u4e4b\u540e\u7684\u65b0\u8bed\u6cd5 \u8fd9\u91cc\u7684 “\u5b8c\u5168” \u662f\u6307\u672c\u6587\u5c3d\u53ef\u80fd\u9f50\u5168 \u8fd9\u91cc\u7684 &#8220…<\/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-1353","post","type-post","status-publish","format-standard","hentry","category-learn"],"_links":{"self":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1353"}],"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=1353"}],"version-history":[{"count":1,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1353\/revisions"}],"predecessor-version":[{"id":1459,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1353\/revisions\/1459"}],"wp:attachment":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1353"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1353"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1353"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}