{"id":1369,"date":"2024-06-02T22:24:59","date_gmt":"2024-06-02T22:24:59","guid":{"rendered":""},"modified":"2024-06-05T03:09:46","modified_gmt":"2024-06-04T19:09:46","slug":"underscore-%e7%b3%bb%e5%88%97%e4%b9%8b%e5%86%85%e9%83%a8%e5%87%bd%e6%95%b0-cb-%e5%92%8c-optimizecb","status":"publish","type":"post","link":"https:\/\/www.lccc.top\/?p=1369","title":{"rendered":"underscore \u7cfb\u5217\u4e4b\u5185\u90e8\u51fd\u6570 cb \u548c optimizeCb"},"content":{"rendered":"\n

\u524d\u8a00<\/h2>\n

\u4ec5\u770b cb \u548c optimizeCb \u4e24\u4e2a\u51fd\u6570\u7684\u540d\u5b57\uff0c\u4f60\u53ef\u80fd\u60f3\u4e0d\u5230\u8fd9\u662f\u7528\u6765\u505a\u4ec0\u4e48\u7684\uff0c\u5c3d\u7ba1\u4f60\u53ef\u80fd\u60f3\u5230 cb \u662f callback \u7684\u7f29\u5199\u3002<\/p>\n

\u5982\u679c\u76f4\u63a5\u8bb2\u89e3\u6e90\u7801\uff0c\u4f60\u53ef\u80fd\u60f3\u4e0d\u660e\u767d\u4e3a\u4ec0\u4e48\u8981\u8fd9\u4e48\u5199\uff0c\u6240\u4ee5\u6211\u4eec\u4ece _.map \u51fd\u6570\u5f00\u59cb\u8bb2\u8d77\u3002<\/p>\n

_.map<\/h2>\n

_.map \u7c7b\u4f3c\u4e8e Array.prototype.map<\/code>\uff0c\u4f46\u66f4\u52a0\u5065\u58ee\u548c\u5b8c\u5584\u3002\u6211\u4eec\u770b\u4e0b _.map \u7684\u6e90\u7801\uff1a<\/p>\n

<\/p>\n
\/\/ \u7b80\u5316\u8fc7\uff0c\u8fd9\u91cc\u4ec5\u5047\u8bbe obj \u662f\u6570\u7ec4<\/span>\n_<\/span>.<\/span>map<\/span> =<\/span> function<\/span> (<\/span>obj<\/span>,<\/span> iteratee<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n    iteratee<\/span> =<\/span> cb<\/span>(<\/span>iteratee<\/span>,<\/span> context<\/span>)<\/span>;<\/span>\n\n    var<\/span> length<\/span> =<\/span> obj<\/span>.<\/span>length<\/span>,<\/span> results<\/span> =<\/span> Array<\/span>(<\/span>length<\/span>)<\/span>;<\/span>\n    for<\/span> (<\/span>var<\/span> index<\/span> =<\/span> 0<\/span>;<\/span> index<\/span> <<\/span> length<\/span>;<\/span> index<\/span>++<\/span>)<\/span> {<\/span>\n        results<\/span>[<\/span>index<\/span>]<\/span> =<\/span> iteratee<\/span>(<\/span>obj<\/span>[<\/span>index<\/span>]<\/span>,<\/span> index<\/span>,<\/span> obj<\/span>)<\/span>;<\/span>\n    }<\/span>\n\n    return<\/span> results<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
map \u65b9\u6cd5\u9664\u4e86\u4f20\u5165\u8981\u5904\u7406\u7684\u6570\u7ec4\u4e4b\u5916\uff0c\u8fd8\u6709\u4e24\u4e2a\u53c2\u6570 iteratee \u548c context\uff0c\u7c7b\u4f3c\u4e8e Array.prototype.map<\/code> \u4e2d\u7684\u5176\u4ed6\u4e24\u4e2a\u53c2\u6570\uff0c\u5176\u4e2d iteratee \u8868\u793a\u5904\u7406\u51fd\u6570\uff0ccontext \u8868\u793a\u6307\u5b9a\u7684\u6267\u884c\u4e0a\u4e0b\u6587\uff0c\u5373 this \u7684\u503c\u3002<\/p>\n
\u7136\u540e\u5728\u6e90\u7801\u4e2d\uff0c\u6211\u4eec\u770b\u5230\uff0c\u6211\u4eec\u5c06 iteratee \u548c context \u4f20\u5165\u4e00\u4e2a cb \u51fd\u6570\uff0c\u7136\u540e\u8986\u76d6\u6389 iteratee \u51fd\u6570\uff0c\u7136\u540e\u5c06\u8fd9\u4e2a\u51fd\u6570\u7528\u4f5c\u6700\u7ec8\u7684\u5904\u7406\u51fd\u6570\u3002<\/p>\n
\u5b9e\u9645\u4e0a\uff0c\u9700\u8981\u8fd9\u4e48\u9ebb\u70e6\u5417\uff1f\u4e0d\u5c31\u662f\u4f7f\u7528 iteratee \u51fd\u6570\u5904\u7406\u6bcf\u6b21\u8fed\u4ee3\u7684\u503c\u5417\uff1f\u4e0d\u5c31\u662f\u901a\u8fc7 context \u6307\u5b9a this \u7684\u503c\u5417\uff1f\u6211\u4eec\u53ef\u4ee5\u76f4\u63a5\u8fd9\u6837\u5199\u5450\uff1a<\/p>\n
<\/p>\n
_<\/span>.<\/span>map<\/span> =<\/span> function<\/span> (<\/span>obj<\/span>,<\/span> iteratee<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n    var<\/span> length<\/span> =<\/span> obj<\/span>.<\/span>length<\/span>,<\/span> results<\/span> =<\/span> Array<\/span>(<\/span>length<\/span>)<\/span>;<\/span>\n    for<\/span> (<\/span>var<\/span> index<\/span> =<\/span> 0<\/span>;<\/span> index<\/span> <<\/span> length<\/span>;<\/span> index<\/span>++<\/span>)<\/span> {<\/span>\n        results<\/span>[<\/span>index<\/span>]<\/span> =<\/span> iteratee<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> obj<\/span>[<\/span>index<\/span>]<\/span>,<\/span> index<\/span>,<\/span> obj<\/span>)<\/span>;<\/span>\n    }<\/span>\n    return<\/span> results<\/span>;<\/span>\n}<\/span>;<\/span>\n\n\/\/ [2, 3, 4]<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>_<\/span>.<\/span>map<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> function<\/span>(<\/span>item<\/span>)<\/span>{<\/span>\n    return<\/span> item<\/span> +<\/span> 1<\/span>;<\/span>\n}<\/span>)<\/span>)<\/span> \n\n\/\/ [2, 3, 4]<\/span>\nconsole<\/span>.<\/span>log<\/span>(<\/span>_<\/span>.<\/span>map<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> function<\/span>(<\/span>item<\/span>)<\/span>{<\/span>\n    return<\/span> item<\/span> +<\/span> this<\/span>.<\/span>value<\/span>;<\/span>\n}<\/span>,<\/span> {<\/span>value<\/span>: 1<\/span>}<\/span>)<\/span>)<\/span> <\/pre>\n<\/div>\n
\u4f60\u770b\u770b\u4e5f\u6ca1\u6709\u4ec0\u4e48\u95ee\u9898\u5450\uff0c\u53ef\u662f\uff0c\u4e07\u4e00 iteratee \u6211\u4eec\u4e0d\u4f20\u5165\u4e00\u4e2a\u51fd\u6570\u5462\uff1f\u6bd4\u5982\u6211\u4eec\u4ec0\u4e48\u4e5f\u4e0d\u4f20\uff0c\u6216\u8005\u4f20\u5165\u4e00\u4e2a\u5bf9\u8c61\uff0c\u53c8\u6216\u8005\u4f20\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32\u3001\u6570\u5b57\u5462\uff1f<\/p>\n
\u5982\u679c\u7528\u6211\u4eec\u7684\u65b9\u6cd5\u81ea\u7136\u662f\u4f1a\u62a5\u9519\u7684\uff0c\u90a3 underscore \u5462\uff1f<\/p>\n
<\/p>\n
\/\/ \u4f7f\u7528 underscore<\/span>\n\n\/\/ \u4ec0\u4e48\u4e5f\u4e0d\u4f20<\/span>\nvar<\/span> result<\/span> =<\/span> _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>1<\/span>,<\/span>2<\/span>,<\/span>3<\/span>]<\/span>)<\/span>;<\/span> \/\/ [1, 2, 3]<\/span>\n\n\/\/ \u4f20\u5165\u4e00\u4e2a\u5bf9\u8c61<\/span>\nvar<\/span> result<\/span> =<\/span> _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>{<\/span>name<\/span>:'Kevin'<\/span>}<\/span>,<\/span> {<\/span>name<\/span>: 'Daisy'<\/span>,<\/span> age<\/span>: 18<\/span>}<\/span>]<\/span>,<\/span> {<\/span>name<\/span>: 'Daisy'<\/span>}<\/span>)<\/span>;<\/span> \/\/ [false, true]<\/span>\n\nvar<\/span> result<\/span> =<\/span> _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>{<\/span>name<\/span>: 'Kevin'<\/span>}<\/span>,<\/span> {<\/span>name<\/span>: 'Daisy'<\/span>}<\/span>]<\/span>,<\/span> 'name'<\/span>)<\/span>;<\/span> \/\/ ['Kevin', 'daisy']<\/span><\/pre>\n<\/div>\n
\u6211\u4eec\u4f1a\u53d1\u73b0\uff0cunderscore \u7adf\u7136\u8fd8\u80fd\u6839\u636e\u4f20\u5165\u7684\u503c\u7684\u7c7b\u578b\u4e0d\u540c\uff0c\u5b9e\u73b0\u7684\u6548\u679c\u4e0d\u540c\u3002\u6211\u4eec\u603b\u7ed3\u4e0b\uff1a<\/p>\n
    \n
  1. \u5f53 iteratee \u4e0d\u4f20\u65f6\uff0c\u8fd4\u56de\u4e00\u4e2a\u76f8\u540c\u7684\u6570\u7ec4\u3002<\/li>\n
  2. \u5f53 iteratee \u4e3a\u4e00\u4e2a\u51fd\u6570\uff0c\u6b63\u5e38\u5904\u7406\u3002<\/li>\n
  3. \u5f53 iteratee \u4e3a\u4e00\u4e2a\u5bf9\u8c61\uff0c\u8fd4\u56de\u5143\u7d20\u662f\u5426\u5339\u914d\u6307\u5b9a\u7684\u5bf9\u8c61\u3002<\/li>\n
  4. \u5f53 iteratee \u4e3a\u5b57\u7b26\u4e32\uff0c\u8fd4\u56de\u5143\u7d20\u5bf9\u5e94\u7684\u5c5e\u6027\u503c\u7684\u96c6\u5408\u3002<\/li>\n<\/ol>\n
    \u7531\u6b64\uff0c\u6211\u4eec\u53ef\u4ee5\u63a8\u6d4b\u5728 underscore \u7684 cb \u51fd\u6570\u4e2d\uff0c\u6709\u5bf9 iteratee \u503c\u7c7b\u578b\u7684\u5224\u65ad\uff0c\u7136\u540e\u6839\u636e\u4e0d\u540c\u7684\u7c7b\u578b\uff0c\u8fd4\u56de\u4e0d\u540c\u7684 iteratee \u51fd\u6570\u3002<\/p>\n
    cb<\/h2>\n
    \u6240\u4ee5\u6211\u4eec\u6765\u770b\u770b cb \u51fd\u6570\u7684\u6e90\u7801\uff1a<\/p>\n
    <\/p>\n
    var<\/span> cb<\/span> =<\/span> function<\/span>(<\/span>value<\/span>,<\/span> context<\/span>,<\/span> argCount<\/span>)<\/span> {<\/span>\n    \n    if<\/span> (<\/span>_<\/span>.<\/span>iteratee<\/span> !==<\/span> builtinIteratee<\/span>)<\/span> return<\/span> _<\/span>.<\/span>iteratee<\/span>(<\/span>value<\/span>,<\/span> context<\/span>)<\/span>;<\/span>\n\n    if<\/span> (<\/span>value<\/span> ==<\/span> null<\/span>)<\/span> return<\/span> _<\/span>.<\/span>identity<\/span>;<\/span>\n\n    if<\/span> (<\/span>_<\/span>.<\/span>isFunction<\/span>(<\/span>value<\/span>)<\/span>)<\/span> return<\/span> optimizeCb<\/span>(<\/span>value<\/span>,<\/span> context<\/span>,<\/span> argCount<\/span>)<\/span>;<\/span>\n\n    if<\/span> (<\/span>_<\/span>.<\/span>isObject<\/span>(<\/span>value<\/span>)<\/span> &&<\/span> !<\/span>_<\/span>.<\/span>isArray<\/span>(<\/span>value<\/span>)<\/span>)<\/span> return<\/span> _<\/span>.<\/span>matcher<\/span>(<\/span>value<\/span>)<\/span>;<\/span>\n\n    return<\/span> _<\/span>.<\/span>property<\/span>(<\/span>value<\/span>)<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
    \u8fd9\u4e00\u770b\u5c31\u7275\u626f\u5230\u4e86 8 \u4e2a\u51fd\u6570\uff01\u4e0d\u8981\u5bb3\u6015\uff0c\u6211\u4eec\u4e00\u4e2a\u4e00\u4e2a\u770b\u3002<\/p>\n
    _.iteratee<\/h2>\n
    \n
    if<\/span> (<\/span>_<\/span>.<\/span>iteratee<\/span> !==<\/span> builtinIteratee<\/span>)<\/span> return<\/span> _<\/span>.<\/span>iteratee<\/span>(<\/span>value<\/span>,<\/span> context<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
    \u6211\u4eec\u770b\u770b _.iteratee \u7684\u6e90\u7801\uff1a<\/p>\n
    <\/p>\n
    _<\/span>.<\/span>iteratee<\/span> =<\/span> builtinIteratee<\/span> =<\/span> function<\/span>(<\/span>value<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n    return<\/span> cb<\/span>(<\/span>value<\/span>,<\/span> context<\/span>,<\/span> Infinity<\/span>)<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
    \u56e0\u4e3a _.iteratee = builtinIteratee<\/code> \u7684\u7f18\u6545\uff0c_.iteratee !== builtinIteratee<\/code> \u503c\u4e3a false\uff0c\u6240\u4ee5\u6b63\u5e38\u60c5\u51b5\u4e0b _.iteratee(value, context)<\/code> \u5e76\u4e0d\u4f1a\u6267\u884c\u3002<\/p>\n
    \u4f46\u662f\u5982\u679c\u6211\u4eec\u5728\u5916\u90e8\u4fee\u6539\u4e86 _.iteratee \u51fd\u6570\uff0c\u7ed3\u679c\u4fbf\u4f1a\u4e3a true\uff0ccb \u51fd\u6570\u76f4\u63a5\u8fd4\u56de _.iteratee(value, context)<\/code>\u3002<\/p>\n
    \u8fd9\u4e2a\u610f\u601d\u5176\u5b9e\u662f\u8bf4\u7528\u6211\u4eec\u81ea\u5b9a\u4e49\u7684 _.iteratee \u51fd\u6570\u6765\u5904\u7406 value \u548c context\u3002<\/p>\n
    \u8bd5\u60f3\u6211\u4eec\u5e76\u4e0d\u9700\u8981\u73b0\u5728 _.map \u8fd9\u4e48\u5f3a\u5927\u7684\u529f\u80fd\uff0c\u6211\u53ea\u5e0c\u671b\u5f53 value \u662f\u4e00\u4e2a\u51fd\u6570\uff0c\u5c31\u7528\u8be5\u51fd\u6570\u5904\u7406\u6570\u7ec4\u5143\u7d20\uff0c\u5982\u679c\u4e0d\u662f\u51fd\u6570\uff0c\u5c31\u76f4\u63a5\u8fd4\u56de\u5f53\u524d\u5143\u7d20\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u4fee\u6539\uff1a<\/p>\n
    <\/p>\n
    <<\/span>html<\/span>><\/span>\n<<\/span>head<\/span>><\/span>\n    <<\/span>title<\/span>><\/span>underscore map<\/<\/span>title<\/span>><\/span>\n<\/<\/span>head<\/span>><\/span>\n<<\/span>body<\/span>><\/span>\n    <<\/span>script<\/span> src<\/span>=\"..\/vender\/underscore.js<\/span>\"><\/span><\/<\/span>script<\/span>><\/span>\n    <<\/span>script<\/span> type<\/span>=\"text\/javascript<\/span>\"><\/span>\n    _<\/span>.<\/span>iteratee<\/span> =<\/span> function<\/span>(<\/span>value<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n        if<\/span> (<\/span>typeof<\/span> value<\/span> ===<\/span> 'function'<\/span>)<\/span> {<\/span>\n            return<\/span> function<\/span>(<\/span>...rest<\/span>)<\/span> {<\/span>\n                return<\/span> value<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> ...rest<\/span>)<\/span>\n            }<\/span>;<\/span>\n        }<\/span>\n        return<\/span> function<\/span>(<\/span>value<\/span>)<\/span> {<\/span>\n            return<\/span> value<\/span>;<\/span>\n        }<\/span>;<\/span>\n    }<\/span>;<\/span>\n\n    \/\/ \u5982\u679c map \u7684\u7b2c\u4e8c\u4e2a\u53c2\u6570\u4e0d\u662f\u51fd\u6570\uff0c\u5c31\u8fd4\u56de\u8be5\u5143\u7d20<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>_<\/span>.<\/span>map<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> 'name'<\/span>)<\/span>)<\/span>;<\/span> \/\/ [1, 2, 3]<\/span>\n\n    \/\/ \u5982\u679c map \u7684\u7b2c\u4e8c\u4e2a\u53c2\u6570\u662f\u51fd\u6570\uff0c\u5c31\u4f7f\u7528\u8be5\u51fd\u6570\u5904\u7406\u6570\u7ec4\u5143\u7d20<\/span>\n    var<\/span> result<\/span> =<\/span> _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>,<\/span> function<\/span>(<\/span>item<\/span>)<\/span> {<\/span>\n        return<\/span> item<\/span> +<\/span> 1<\/span>;<\/span>\n    }<\/span>)<\/span>;<\/span>\n\n    console<\/span>.<\/span>log<\/span>(<\/span>result<\/span>)<\/span>;<\/span> \/\/ [2, 3, 4]<\/span>\n    <\/<\/span>script<\/span>><\/span>\n<\/<\/span>body<\/span>><\/span>\n<\/<\/span>html<\/span>><\/span><\/pre>\n<\/div>\n
    \u5f53\u7136\u66f4\u591a\u7684\u60c5\u51b5\u662f\u81ea\u5b9a\u4e49\u5bf9\u4e0d\u540c\u7684 value \u4f7f\u7528\u4e0d\u540c\u7684\u5904\u7406\u51fd\u6570\uff0c\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0cunderscore \u4e2d\u7684\u591a\u4e2a\u51fd\u6570\u90fd\u662f\u7528\u4e86 cb \u51fd\u6570\uff0c\u800c\u56e0\u4e3a cb \u51fd\u6570\u4f7f\u7528\u4e86 _.iteratee \u51fd\u6570\uff0c\u5982\u679c\u4f60\u4fee\u6539\u8fd9\u4e2a\u51fd\u6570\uff0c\u5176\u5b9e\u4f1a\u5f71\u54cd\u591a\u4e2a\u51fd\u6570\uff0c\u8fd9\u4e9b\u51fd\u6570\u57fa\u672c\u90fd\u5c5e\u4e8e\u96c6\u5408\u51fd\u6570\uff0c\u5177\u4f53\u5305\u62ec map\u3001find\u3001filter\u3001reject\u3001every\u3001some\u3001max\u3001min\u3001sortBy\u3001groupBy\u3001indexBy\u3001countBy\u3001sortedIndex\u3001partition\u3001\u548c unique\u3002<\/p>\n
    _.identity<\/h2>\n
    \n
    if<\/span> (<\/span>value<\/span> ==<\/span> null<\/span>)<\/span> return<\/span> _<\/span>.<\/span>identity<\/span>;<\/span><\/pre>\n<\/div>\n
    \u8ba9\u6211\u4eec\u770b\u770b _.identity \u7684\u6e90\u7801\uff1a<\/p>\n
    <\/p>\n
    _<\/span>.<\/span>identity<\/span> =<\/span> function<\/span>(<\/span>value<\/span>)<\/span> {<\/span>\n    return<\/span> value<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
    \u8fd9\u4e5f\u5c31\u662f\u4e3a\u4ec0\u4e48\u5f53 map \u7684\u7b2c\u4e8c\u4e2a\u53c2\u6570\u4ec0\u4e48\u90fd\u4e0d\u4f20\u7684\u65f6\u5019\uff0c\u7ed3\u679c\u4f1a\u662f\u4e00\u4e2a\u76f8\u540c\u6570\u7ec4\u7684\u539f\u56e0\u3002<\/p>\n
    \n
    _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>1<\/span>,<\/span>2<\/span>,<\/span>3<\/span>]<\/span>)<\/span>;<\/span> \/\/ [1, 2, 3]<\/span><\/pre>\n<\/div>\n
    \u5982\u679c\u76f4\u63a5\u770b\u8fd9\u4e2a\u51fd\u6570\uff0c\u53ef\u80fd\u89c9\u5f97\u6ca1\u6709\u4ec0\u4e48\u7528\uff0c\u4f46\u7528\u5728\u8fd9\u91cc\uff0c\u5374\u53c8\u5341\u5206\u7684\u5408\u9002\u3002<\/p>\n
    optimizeCb<\/h2>\n
    \n
    if<\/span> (<\/span>_<\/span>.<\/span>isFunction<\/span>(<\/span>value<\/span>)<\/span>)<\/span> return<\/span> optimizeCb<\/span>(<\/span>value<\/span>,<\/span> context<\/span>,<\/span> argCount<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
    \u5f53 value \u662f\u4e00\u4e2a\u51fd\u6570\u7684\u65f6\u5019\uff0c\u5c31\u4f20\u5165 optimizeCb \u51fd\u6570\uff0c\u6211\u4eec\u6765\u770b\u770b optimizeCb \u51fd\u6570\uff1a<\/p>\n
    <\/p>\n
    var<\/span> optimizeCb<\/span> =<\/span> function<\/span>(<\/span>func<\/span>,<\/span> context<\/span>,<\/span> argCount<\/span>)<\/span> {<\/span>\n    \/\/ \u5982\u679c\u6ca1\u6709\u4f20\u5165 context\uff0c\u5c31\u8fd4\u56de func \u51fd\u6570<\/span>\n    if<\/span> (<\/span>context<\/span> ===<\/span> void<\/span> 0<\/span>)<\/span> return<\/span> func<\/span>;<\/span>\n    switch<\/span> (<\/span>argCount<\/span>)<\/span> {<\/span>\n        case<\/span> 1<\/span>:\n            return<\/span> function<\/span>(<\/span>value<\/span>)<\/span> {<\/span>\n                return<\/span> func<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> value<\/span>)<\/span>;<\/span>\n            }<\/span>;<\/span>\n        case<\/span> null<\/span>:\n        case<\/span> 3<\/span>:\n            return<\/span> function<\/span>(<\/span>value<\/span>,<\/span> index<\/span>,<\/span> collection<\/span>)<\/span> {<\/span>\n                return<\/span> func<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> value<\/span>,<\/span> index<\/span>,<\/span> collection<\/span>)<\/span>;<\/span>\n            }<\/span>;<\/span>\n        case<\/span> 4<\/span>:\n            return<\/span> function<\/span>(<\/span>accumulator<\/span>,<\/span> value<\/span>,<\/span> index<\/span>,<\/span> collection<\/span>)<\/span> {<\/span>\n                return<\/span> func<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> accumulator<\/span>,<\/span> value<\/span>,<\/span> index<\/span>,<\/span> collection<\/span>)<\/span>;<\/span>\n            }<\/span>;<\/span>\n    }<\/span>\n    return<\/span> function<\/span>(<\/span>)<\/span> {<\/span>\n        return<\/span> func<\/span>.<\/span>apply<\/span>(<\/span>context<\/span>,<\/span> arguments<\/span>)<\/span>;<\/span>\n    }<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
    \u4e5f\u8bb8\u4f60\u4f1a\u597d\u5947\uff0c\u4e3a\u4ec0\u4e48\u6211\u8981\u5bf9 argCount \u8fdb\u884c\u5224\u65ad\u5462\uff1f\u5c31\u4e0d\u80fd\u76f4\u63a5\u8fd4\u56de\u5417\uff1f\u6bd4\u5982\u8fd9\u6837\uff1a<\/p>\n
    <\/p>\n
    var<\/span> optimizeCb<\/span> =<\/span> function<\/span>(<\/span>func<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n    \/\/ \u5982\u679c\u6ca1\u6709\u4f20\u5165 context\uff0c\u5c31\u8fd4\u56de func \u51fd\u6570<\/span>\n    if<\/span> (<\/span>context<\/span> ===<\/span> void<\/span> 0<\/span>)<\/span> return<\/span> func<\/span>;<\/span>\n    return<\/span> function<\/span>(<\/span>)<\/span> {<\/span>\n        return<\/span> func<\/span>.<\/span>apply<\/span>(<\/span>context<\/span>,<\/span> arguments<\/span>)<\/span>;<\/span>\n    }<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
    \u5f53\u7136\u6ca1\u6709\u95ee\u9898\uff0c\u4f46\u4e3a\u4ec0\u4e48 underscore \u8981\u8fd9\u6837\u505a\u5462\uff1f\u5176\u5b9e\u5c31\u662f\u4e3a\u4e86\u907f\u514d\u4f7f\u7528 arguments\uff0c\u63d0\u9ad8\u4e00\u70b9\u6027\u80fd\u800c\u5df2\uff0c\u5982\u679c\u4e0d\u662f\u5199\u4e00\u4e2a\u5e93\uff0c\u5176\u5b9e\u8fd8\u771f\u662f\u6ca1\u6709\u5fc5\u8981\u505a\u5230\u8fd9\u70b9\u3002<\/p>\n
    \u800c\u4e3a\u4ec0\u4e48\u5f53\u53c2\u6570\u662f 3 \u4e2a\u65f6\u5019\uff0c\u53c2\u6570\u540d\u79f0\u5206\u522b\u662f value, index, collection \uff0c\u53c8\u4e3a\u4ec0\u4e48\u6ca1\u6709\u53c2\u6570\u4e3a 2 \u7684\u60c5\u51b5\u5462\uff1f\u5176\u5b9e\u8fd9\u90fd\u662f\u6839\u636e underscore \u51fd\u6570\u7528\u5230\u7684\u60c5\u51b5\uff0c\u6ca1\u6709\u51fd\u6570\u7528\u5230\u4e24\u4e2a\u53c2\u6570\uff0c\u4e8e\u662f\u5c31\u7701\u7565\u4e86\uff0c\u50cf map \u51fd\u6570\u5c31\u4f1a\u7528\u5230 3 \u4e2a\u53c2\u6570\uff0c\u5c31\u6839\u636e\u8fd9\u4e09\u4e2a\u53c2\u6570\u7684\u540d\u5b57\u8d77\u4e86\u8fd9\u91cc\u7684\u53d8\u91cf\u540d\u5566\u3002<\/p>\n
    _.matcher<\/h2>\n
    \n
    if<\/span> (<\/span>_<\/span>.<\/span>isObject<\/span>(<\/span>value<\/span>)<\/span> &&<\/span> !<\/span>_<\/span>.<\/span>isArray<\/span>(<\/span>value<\/span>)<\/span>)<\/span> return<\/span> _<\/span>.<\/span>matcher<\/span>(<\/span>value<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
    \u8fd9\u6bb5\u5c31\u662f\u7528\u6765\u5904\u7406\u5f53 map \u7684\u7b2c\u4e8c\u4e2a\u53c2\u6570\u662f\u5bf9\u8c61\u7684\u60c5\u51b5\uff1a<\/p>\n
    <\/p>\n
    \/\/ \u4f20\u5165\u4e00\u4e2a\u5bf9\u8c61<\/span>\nvar<\/span> result<\/span> =<\/span> _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>{<\/span>name<\/span>:'Kevin'<\/span>}<\/span>,<\/span> {<\/span>name<\/span>: 'Daisy'<\/span>,<\/span> age<\/span>: 18<\/span>}<\/span>]<\/span>,<\/span> {<\/span>name<\/span>: 'Daisy'<\/span>}<\/span>)<\/span>;<\/span> \/\/ [false, true]<\/span><\/pre>\n<\/div>\n
    \u5982\u679c value \u662f\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5e76\u4e14\u4e0d\u662f\u6570\u7ec4\uff0c\u5c31\u4f7f\u7528 _.matcher \u51fd\u6570\u3002\u770b\u770b\u5404\u4e2a\u51fd\u6570\u7684\u6e90\u7801\uff1a<\/p>\n
    <\/p>\n
    var<\/span> nativeIsArray<\/span> =<\/span> Array<\/span>.<\/span>isArray<\/span>;<\/span>\n\n_<\/span>.<\/span>isArray<\/span> =<\/span> nativeIsArray<\/span> ||<\/span> function<\/span>(<\/span>obj<\/span>)<\/span> {<\/span>\n    return<\/span> Object<\/span>.<\/span>prototype<\/span>.<\/span>toString<\/span>.<\/span>call<\/span>(<\/span>obj<\/span>)<\/span> ===<\/span> '[object Array]'<\/span>;<\/span>\n}<\/span>;<\/span>\n\n_<\/span>.<\/span>isObject<\/span> =<\/span> function<\/span>(<\/span>obj<\/span>)<\/span> {<\/span>\n    var<\/span> type<\/span> =<\/span> typeof<\/span> obj<\/span>;<\/span>\n    return<\/span> type<\/span> ===<\/span> 'function'<\/span> ||<\/span> type<\/span> ===<\/span> 'object'<\/span> &&<\/span> !<\/span>!<\/span>obj<\/span>;<\/span>\n}<\/span>;<\/span>\n\n\n\/\/ extend \u51fd\u6570\u53ef\u4ee5\u53c2\u8003 \u300aJavaScript \u4e13\u9898\u4e4b\u624b\u5199\u4e00\u4e2a jQuery \u7684 extend\u300b<\/span>\n_<\/span>.<\/span>matcher<\/span> =<\/span> function<\/span>(<\/span>attrs<\/span>)<\/span> {<\/span>\n    attrs<\/span> =<\/span> _<\/span>.<\/span>extend<\/span>(<\/span>{<\/span>}<\/span>,<\/span> attrs<\/span>)<\/span>;<\/span>\n    return<\/span> function<\/span>(<\/span>obj<\/span>)<\/span> {<\/span>\n      return<\/span> _<\/span>.<\/span>isMatch<\/span>(<\/span>obj<\/span>,<\/span> attrs<\/span>)<\/span>;<\/span>\n    }<\/span>;<\/span>\n}<\/span>;<\/span>\n\n\/\/ \u8be5\u51fd\u6570\u5224\u65ad attr \u5bf9\u8c61\u4e2d\u7684\u952e\u503c\u662f\u5426\u5728 object \u4e2d\u6709\u5e76\u4e14\u76f8\u7b49<\/span>\n\n\/\/ var stooge = {name: 'moe', age: 32};<\/span>\n\/\/ _.isMatch(stooge, {age: 32}); => true<\/span>\n\n\/\/ \u5176\u4e2d _.keys \u76f8\u5f53\u4e8e Object.keys<\/span>\n_<\/span>.<\/span>isMatch<\/span> =<\/span> function<\/span>(<\/span>object<\/span>,<\/span> attrs<\/span>)<\/span> {<\/span>\n    var<\/span> keys<\/span> =<\/span> _<\/span>.<\/span>keys<\/span>(<\/span>attrs<\/span>)<\/span>,<\/span> length<\/span> =<\/span> keys<\/span>.<\/span>length<\/span>;<\/span>\n    if<\/span> (<\/span>object<\/span> ==<\/span> null<\/span>)<\/span> return<\/span> !<\/span>length<\/span>;<\/span>\n    var<\/span> obj<\/span> =<\/span> Object<\/span>(<\/span>object<\/span>)<\/span>;<\/span>\n    for<\/span> (<\/span>var<\/span> i<\/span> =<\/span> 0<\/span>;<\/span> i<\/span> <<\/span> length<\/span>;<\/span> i<\/span>++<\/span>)<\/span> {<\/span>\n        var<\/span> key<\/span> =<\/span> keys<\/span>[<\/span>i<\/span>]<\/span>;<\/span>\n        if<\/span> (<\/span>attrs<\/span>[<\/span>key<\/span>]<\/span> !==<\/span> obj<\/span>[<\/span>key<\/span>]<\/span> ||<\/span> !<\/span>(<\/span>key<\/span> in<\/span> obj<\/span>)<\/span>)<\/span> return<\/span> false<\/span>;<\/span>\n    }<\/span>\n    return<\/span> true<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
    _.property<\/h2>\n
    \n
    return<\/span> _<\/span>.<\/span>property<\/span>(<\/span>value<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
    \u8fd9\u4e2a\u5c31\u662f\u5904\u7406\u5f53 value \u662f\u57fa\u672c\u7c7b\u578b\u7684\u503c\u7684\u65f6\u5019\uff0c\u8fd4\u56de\u5143\u7d20\u5bf9\u5e94\u7684\u5c5e\u6027\u503c\u7684\u60c5\u51b5\uff1a<\/p>\n
    \n
    var<\/span> result<\/span> =<\/span> _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>{<\/span>name<\/span>: 'Kevin'<\/span>}<\/span>,<\/span> {<\/span>name<\/span>: 'Daisy'<\/span>}<\/span>]<\/span>,<\/span> 'name'<\/span>)<\/span>;<\/span> \/\/ ['Kevin', 'daisy']<\/span><\/pre>\n<\/div>\n
    \u6211\u4eec\u770b\u4e0b\u6e90\u7801\uff1a<\/p>\n
    <\/p>\n
    _<\/span>.<\/span>property<\/span> =<\/span> function<\/span>(<\/span>path<\/span>)<\/span> {<\/span>\n    \/\/ \u5982\u679c\u4e0d\u662f\u6570\u7ec4<\/span>\n    if<\/span> (<\/span>!<\/span>_<\/span>.<\/span>isArray<\/span>(<\/span>path<\/span>)<\/span>)<\/span> {<\/span>\n      return<\/span> shallowProperty<\/span>(<\/span>path<\/span>)<\/span>;<\/span>\n    }<\/span>\n    return<\/span> function<\/span>(<\/span>obj<\/span>)<\/span> {<\/span>\n        return<\/span> deepGet<\/span>(<\/span>obj<\/span>,<\/span> path<\/span>)<\/span>;<\/span>\n    }<\/span>;<\/span>\n}<\/span>;<\/span>\n\nvar<\/span> shallowProperty<\/span> =<\/span> function<\/span>(<\/span>key<\/span>)<\/span> {<\/span>\n    return<\/span> function<\/span>(<\/span>obj<\/span>)<\/span> {<\/span>\n        return<\/span> obj<\/span> ==<\/span> null<\/span> ? void<\/span> 0<\/span> : obj<\/span>[<\/span>key<\/span>]<\/span>;<\/span>\n    }<\/span>;<\/span>\n}<\/span>;<\/span>\n\n\/\/ \u6839\u636e\u8def\u5f84\u53d6\u51fa\u6df1\u5c42\u6b21\u7684\u503c<\/span>\nvar<\/span> deepGet<\/span> =<\/span> function<\/span>(<\/span>obj<\/span>,<\/span> path<\/span>)<\/span> {<\/span>\n    var<\/span> length<\/span> =<\/span> path<\/span>.<\/span>length<\/span>;<\/span>\n    for<\/span> (<\/span>var<\/span> i<\/span> =<\/span> 0<\/span>;<\/span> i<\/span> <<\/span> length<\/span>;<\/span> i<\/span>++<\/span>)<\/span> {<\/span>\n        if<\/span> (<\/span>obj<\/span> ==<\/span> null<\/span>)<\/span> return<\/span> void<\/span> 0<\/span>;<\/span>\n        obj<\/span> =<\/span> obj<\/span>[<\/span>path<\/span>[<\/span>i<\/span>]<\/span>]<\/span>;<\/span>\n    }<\/span>\n    return<\/span> length<\/span> ? obj<\/span> : void<\/span> 0<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
    \u6211\u4eec\u597d\u50cf\u53d1\u73b0\u4e86\u65b0\u5927\u9646\uff0c\u539f\u6765 value \u8fd8\u53ef\u4ee5\u4f20\u4e00\u4e2a\u6570\u7ec4\uff0c\u7528\u6765\u53d6\u6df1\u5c42\u6b21\u7684\u503c\uff0c\u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n
    <\/p>\n
    var<\/span> person1<\/span> =<\/span> {<\/span>\n    child<\/span>: {<\/span>\n        nickName<\/span>: 'Kevin'<\/span>\n    }<\/span>\n}<\/span>\n\nvar<\/span> person2<\/span> =<\/span> {<\/span>\n    child<\/span>: {<\/span>\n        nickName<\/span>: 'Daisy'<\/span>\n    }<\/span>\n}<\/span>\n\nvar<\/span> result<\/span> =<\/span> _<\/span>.<\/span>map<\/span>(<\/span>[<\/span>person1<\/span>,<\/span> person2<\/span>]<\/span>,<\/span> [<\/span>'child'<\/span>,<\/span> 'nickName'<\/span>]<\/span>)<\/span>;<\/span> \nconsole<\/span>.<\/span>log<\/span>(<\/span>result<\/span>)<\/span> \/\/ ['Kevin', 'daisy']<\/span><\/pre>\n<\/div>\n
    \u6700\u540e<\/h2>\n
    \u5982\u679c\u4f60\u60f3\u5b66\u4e60 underscore \u7684\u6e90\u7801\uff0c\u5728\u5206\u6790\u96c6\u5408\u76f8\u5173\u7684\u51fd\u6570\u65f6\u4e00\u5b9a\u4f1a\u63a5\u89e6 cb \u548c optimizeCb \u51fd\u6570\uff0c\u5148\u638c\u63e1\u8fd9\u4e24\u4e2a\u51fd\u6570\uff0c\u4f1a\u5e2e\u52a9\u4f60\u66f4\u597d\u66f4\u5feb\u7684\u89e3\u8bfb\u6e90\u7801\u3002<\/p>\n
    underscore \u7cfb\u5217<\/h2>\n
    underscore \u7cfb\u5217\u76ee\u5f55\u5730\u5740\uff1ahttps:\/\/github.com\/mqyqingfeng\/Blog<\/a>\u3002<\/p>\n
    underscore \u7cfb\u5217\u9884\u8ba1\u5199\u516b\u7bc7\u5de6\u53f3\uff0c\u91cd\u70b9\u4ecb\u7ecd underscore \u4e2d\u7684\u4ee3\u7801\u67b6\u6784\u3001\u94fe\u5f0f\u8c03\u7528\u3001\u5185\u90e8\u51fd\u6570\u3001\u6a21\u677f\u5f15\u64ce\u7b49\u5185\u5bb9\uff0c\u65e8\u5728\u5e2e\u52a9\u5927\u5bb6\u9605\u8bfb\u6e90\u7801\uff0c\u4ee5\u53ca\u5199\u51fa\u81ea\u5df1\u7684 undercore\u3002<\/p>\n<\/td>\n
    \u6587\u7ae0\u8f6c\u8f7d\u81eahttps:\/\/github.com\/mqyqingfeng\/Blog\/issues\/58<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
    \u524d\u8a00 \u4ec5\u770b cb \u548c optimizeCb \u4e24\u4e2a\u51fd\u6570\u7684\u540d\u5b57\uff0c\u4f60\u53ef\u80fd\u60f3\u4e0d\u5230\u8fd9\u662f\u7528\u6765\u505a\u4ec0\u4e48\u7684\uff0c\u5c3d\u7ba1\u4f60\u53ef\u80fd\u60f3\u5230 cb \u662f callback \u7684\u7f29\u5199\u3002 \u5982\u679c\u76f4\u63a5\u8bb2\u89e3\u6e90\u7801…<\/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-1369","post","type-post","status-publish","format-standard","hentry","category-learn"],"_links":{"self":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1369"}],"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=1369"}],"version-history":[{"count":1,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1369\/revisions"}],"predecessor-version":[{"id":1472,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1369\/revisions\/1472"}],"wp:attachment":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1369"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1369"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1369"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}