{"id":1374,"date":"2024-06-02T22:28:33","date_gmt":"2024-06-02T22:28:33","guid":{"rendered":""},"modified":"2024-06-05T03:09:46","modified_gmt":"2024-06-04T19:09:46","slug":"javascript%e4%b8%93%e9%a2%98%e4%b9%8b%e5%ad%a6underscore%e5%9c%a8%e6%95%b0%e7%bb%84%e4%b8%ad%e6%9f%a5%e6%89%be%e6%8c%87%e5%ae%9a%e5%85%83%e7%b4%a0","status":"publish","type":"post","link":"https:\/\/www.lccc.top\/?p=1374","title":{"rendered":"JavaScript\u4e13\u9898\u4e4b\u5b66underscore\u5728\u6570\u7ec4\u4e2d\u67e5\u627e\u6307\u5b9a\u5143\u7d20"},"content":{"rendered":"\n

\u524d\u8a00<\/h2>\n

\u5728\u5f00\u53d1\u4e2d\uff0c\u6211\u4eec\u7ecf\u5e38\u4f1a\u9047\u5230\u5728\u6570\u7ec4\u4e2d\u67e5\u627e\u6307\u5b9a\u5143\u7d20\u7684\u9700\u6c42\uff0c\u53ef\u80fd\u5927\u5bb6\u89c9\u5f97\u8fd9\u4e2a\u9700\u6c42\u8fc7\u4e8e\u7b80\u5355\uff0c\u7136\u800c\u5982\u4f55\u4f18\u96c5\u7684\u53bb\u5b9e\u73b0\u4e00\u4e2a findIndex \u548c findLastIndex\u3001indexOf \u548c lastIndexOf \u65b9\u6cd5\u5374\u662f\u5f88\u5c11\u4eba\u53bb\u601d\u8003\u7684\u3002\u672c\u6587\u5c31\u5e26\u7740\u5927\u5bb6\u4e00\u8d77\u53c2\u8003\u7740 underscore \u53bb\u5b9e\u73b0\u8fd9\u4e9b\u65b9\u6cd5\u3002<\/p>\n

\u5728\u5b9e\u73b0\u524d\uff0c\u5148\u770b\u770b ES6 \u7684 findIndex \u65b9\u6cd5\uff0c\u8ba9\u5927\u5bb6\u4e86\u89e3 findIndex \u7684\u4f7f\u7528\u65b9\u6cd5\u3002<\/p>\n

findIndex<\/h2>\n

ES6 \u5bf9\u6570\u7ec4\u65b0\u589e\u4e86 findIndex \u65b9\u6cd5\uff0c\u5b83\u4f1a\u8fd4\u56de\u6570\u7ec4\u4e2d\u6ee1\u8db3\u63d0\u4f9b\u7684\u51fd\u6570\u7684\u7b2c\u4e00\u4e2a\u5143\u7d20\u7684\u7d22\u5f15\uff0c\u5426\u5219\u8fd4\u56de -1\u3002<\/p>\n

\u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n

<\/p>\n
function<\/span> isBigEnough<\/span>(<\/span>element<\/span>)<\/span> {<\/span>\n  return<\/span> element<\/span> >=<\/span> 15<\/span>;<\/span>\n}<\/span>\n\n[<\/span>12<\/span>,<\/span> 5<\/span>,<\/span> 8<\/span>,<\/span> 130<\/span>,<\/span> 44<\/span>]<\/span>.<\/span>findIndex<\/span>(<\/span>isBigEnough<\/span>)<\/span>;<\/span>  \/\/ 3<\/span><\/pre>\n<\/div>\n
findIndex \u4f1a\u627e\u51fa\u7b2c\u4e00\u4e2a\u5927\u4e8e 15 \u7684\u5143\u7d20\u7684\u4e0b\u6807\uff0c\u6240\u4ee5\u6700\u540e\u8fd4\u56de 3\u3002<\/p>\n
\u662f\u4e0d\u662f\u5f88\u7b80\u5355\uff0c\u5176\u5b9e\uff0c\u6211\u4eec\u81ea\u5df1\u53bb\u5b9e\u73b0\u4e00\u4e2a findIndex \u4e5f\u5f88\u7b80\u5355\u3002<\/p>\n
\u5b9e\u73b0findIndex<\/h2>\n
\u601d\u8def\u81ea\u7136\u5f88\u660e\u4e86\uff0c\u904d\u5386\u4e00\u904d\uff0c\u8fd4\u56de\u7b26\u5408\u8981\u6c42\u7684\u503c\u7684\u4e0b\u6807\u5373\u53ef\u3002<\/p>\n
<\/p>\n
function<\/span> findIndex<\/span>(<\/span>array<\/span>,<\/span> predicate<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n    for<\/span> (<\/span>var<\/span> i<\/span> =<\/span> 0<\/span>;<\/span> i<\/span> <<\/span> array<\/span>.<\/span>length<\/span>;<\/span> i<\/span>++<\/span>)<\/span> {<\/span>\n        if<\/span> (<\/span>predicate<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> array<\/span>[<\/span>i<\/span>]<\/span>,<\/span> i<\/span>,<\/span> array<\/span>)<\/span>)<\/span> return<\/span> i<\/span>;<\/span>\n    }<\/span>\n    return<\/span> -<\/span>1<\/span>;<\/span>\n}<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>findIndex<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> 4<\/span>]<\/span>,<\/span> function<\/span>(<\/span>item<\/span>,<\/span> i<\/span>,<\/span> array<\/span>)<\/span>{<\/span>\n    if<\/span> (<\/span>item<\/span> ==<\/span> 3<\/span>)<\/span> return<\/span> true<\/span>;<\/span>\n}<\/span>)<\/span>)<\/span> \/\/ 2<\/span><\/pre>\n<\/div>\n
findLastIndex<\/h2>\n
findIndex \u662f\u6b63\u5e8f\u67e5\u627e\uff0c\u4f46\u6b63\u5982 indexOf \u8fd8\u6709\u4e00\u4e2a\u5bf9\u5e94\u7684 lastIndexOf \u65b9\u6cd5\uff0c\u6211\u4eec\u4e5f\u60f3\u5199\u4e00\u4e2a\u5012\u5e8f\u67e5\u627e\u7684 findLastIndex \u51fd\u6570\u3002\u5b9e\u73b0\u81ea\u7136\u4e5f\u5f88\u7b80\u5355\uff0c\u53ea\u8981\u4fee\u6539\u4e0b\u5faa\u73af\u5373\u53ef\u3002<\/p>\n
<\/p>\n
function<\/span> findLastIndex<\/span>(<\/span>array<\/span>,<\/span> predicate<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n    var<\/span> length<\/span> =<\/span> array<\/span>.<\/span>length<\/span>;<\/span>\n    for<\/span> (<\/span>var<\/span> i<\/span> =<\/span> length<\/span> -<\/span> 1<\/span>;<\/span> i<\/span> >=<\/span> 0<\/span>;<\/span> i<\/span>--<\/span>)<\/span> {<\/span>\n        if<\/span> (<\/span>predicate<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> array<\/span>[<\/span>i<\/span>]<\/span>,<\/span> i<\/span>,<\/span> array<\/span>)<\/span>)<\/span> return<\/span> i<\/span>;<\/span>\n    }<\/span>\n    return<\/span> -<\/span>1<\/span>;<\/span>\n}<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>findLastIndex<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> 4<\/span>]<\/span>,<\/span> function<\/span>(<\/span>item<\/span>,<\/span> index<\/span>,<\/span> array<\/span>)<\/span>{<\/span>\n    if<\/span> (<\/span>item<\/span> ==<\/span> 1<\/span>)<\/span> return<\/span> true<\/span>;<\/span>\n}<\/span>)<\/span>)<\/span> \/\/ 0<\/span><\/pre>\n<\/div>\n
createIndexFinder<\/h2>\n
\u7136\u800c\u95ee\u9898\u5728\u4e8e\uff0cfindIndex \u548c findLastIndex \u5176\u5b9e\u6709\u5f88\u591a\u91cd\u590d\u7684\u90e8\u5206\uff0c\u5982\u4f55\u7cbe\u7b80\u5197\u4f59\u7684\u5185\u5bb9\u5462\uff1f\u8fd9\u4fbf\u662f\u6211\u4eec\u8981\u5b66\u4e60\u7684\u5730\u65b9\uff0c\u65e5\u540e\u9762\u8bd5\u95ee\u5230\u6b64\u7c7b\u95ee\u9898\uff0c\u4e5f\u662f\u52a0\u5206\u7684\u9009\u9879\u3002<\/p>\n
underscore \u7684\u601d\u8def\u5c31\u662f\u5229\u7528\u4f20\u53c2\u7684\u4e0d\u540c\uff0c\u8fd4\u56de\u4e0d\u540c\u7684\u51fd\u6570\u3002\u8fd9\u4e2a\u81ea\u7136\u662f\u7b80\u5355\uff0c\u4f46\u662f\u5982\u4f55\u6839\u636e\u53c2\u6570\u7684\u4e0d\u540c\uff0c\u5728\u540c\u4e00\u4e2a\u5faa\u73af\u4e2d\uff0c\u5b9e\u73b0\u6b63\u5e8f\u548c\u5012\u5e8f\u904d\u5386\u5462\uff1f<\/p>\n
\u8ba9\u6211\u4eec\u76f4\u63a5\u6a21\u4eff underscore \u7684\u5b9e\u73b0\uff1a<\/p>\n
<\/p>\n
function<\/span> createIndexFinder<\/span>(<\/span>dir<\/span>)<\/span> {<\/span>\n    return<\/span> function<\/span>(<\/span>array<\/span>,<\/span> predicate<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n\n        var<\/span> length<\/span> =<\/span> array<\/span>.<\/span>length<\/span>;<\/span>\n        var<\/span> index<\/span> =<\/span> dir<\/span> ><\/span> 0<\/span> ? 0<\/span> : length<\/span> -<\/span> 1<\/span>;<\/span>\n\n        for<\/span> (<\/span>;<\/span> index<\/span> >=<\/span> 0<\/span> &&<\/span> index<\/span> <<\/span> length<\/span>;<\/span> index<\/span> +=<\/span> dir<\/span>)<\/span> {<\/span>\n            if<\/span> (<\/span>predicate<\/span>.<\/span>call<\/span>(<\/span>context<\/span>,<\/span> array<\/span>[<\/span>index<\/span>]<\/span>,<\/span> index<\/span>,<\/span> array<\/span>)<\/span>)<\/span> return<\/span> index<\/span>;<\/span>\n        }<\/span>\n\n        return<\/span> -<\/span>1<\/span>;<\/span>\n    }<\/span>\n}<\/span>\n\nvar<\/span> findIndex<\/span> =<\/span> createIndexFinder<\/span>(<\/span>1<\/span>)<\/span>;<\/span>\nvar<\/span> findLastIndex<\/span> =<\/span> createIndexFinder<\/span>(<\/span>-<\/span>1<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
sortedIndex<\/h2>\n
findIndex \u548c findLastIndex \u7684\u9700\u6c42\u7b97\u662f\u7ed3\u675f\u4e86\uff0c\u4f46\u662f\u53c8\u6765\u4e86\u4e00\u4e2a\u65b0\u9700\u6c42\uff1a\u5728\u4e00\u4e2a\u6392\u597d\u5e8f\u7684\u6570\u7ec4\u4e2d\u627e\u5230 value \u5bf9\u5e94\u7684\u4f4d\u7f6e\uff0c\u4fdd\u8bc1\u63d2\u5165\u6570\u7ec4\u540e\uff0c\u4f9d\u7136\u4fdd\u6301\u6709\u5e8f\u7684\u72b6\u6001\u3002<\/p>\n
\u5047\u8bbe\u8be5\u51fd\u6570\u547d\u540d\u4e3a sortedIndex\uff0c\u6548\u679c\u4e3a\uff1a<\/p>\n
\n
sortedIndex<\/span>(<\/span>[<\/span>10<\/span>,<\/span> 20<\/span>,<\/span> 30<\/span>]<\/span>,<\/span> 25<\/span>)<\/span>;<\/span> \/\/ 2<\/span><\/pre>\n<\/div>\n
\u4e5f\u5c31\u662f\u8bf4\u5982\u679c\uff0c\u6ce8\u610f\u662f\u5982\u679c\uff0c25 \u6309\u7167\u6b64\u4e0b\u6807\u63d2\u5165\u6570\u7ec4\u540e\uff0c\u6570\u7ec4\u53d8\u6210 [10, 20, 25, 30]\uff0c\u6570\u7ec4\u4f9d\u7136\u662f\u6709\u5e8f\u7684\u72b6\u6001\u3002<\/p>\n
\u90a3\u4e48\u8fd9\u4e2a\u53c8\u8be5\u5982\u4f55\u5b9e\u73b0\u5462\uff1f<\/p>\n
\u65e2\u7136\u662f\u6709\u5e8f\u7684\u6570\u7ec4\uff0c\u90a3\u6211\u4eec\u5c31\u4e0d\u9700\u8981\u904d\u5386\uff0c\u5927\u53ef\u4ee5\u4f7f\u7528\u4e8c\u5206\u67e5\u627e\u6cd5\uff0c\u786e\u5b9a\u503c\u7684\u4f4d\u7f6e\u3002\u8ba9\u6211\u4eec\u5c1d\u8bd5\u7740\u53bb\u5199\u4e00\u7248\uff1a<\/p>\n
<\/p>\n
\/\/ \u7b2c\u4e00\u7248<\/span>\nfunction<\/span> sortedIndex<\/span>(<\/span>array<\/span>,<\/span> obj<\/span>)<\/span> {<\/span>\n\n    var<\/span> low<\/span> =<\/span> 0<\/span>,<\/span> high<\/span> =<\/span> array<\/span>.<\/span>length<\/span>;<\/span>\n\n    while<\/span> (<\/span>low<\/span> <<\/span> high<\/span>)<\/span> {<\/span>\n        var<\/span> mid<\/span> =<\/span> Math<\/span>.<\/span>floor<\/span>(<\/span>(<\/span>low<\/span> +<\/span> high<\/span>)<\/span> \/<\/span> 2<\/span>)<\/span>;<\/span>\n        if<\/span> (<\/span>array<\/span>[<\/span>mid<\/span>]<\/span> <<\/span> obj<\/span>)<\/span> low<\/span> =<\/span> mid<\/span> +<\/span> 1<\/span>;<\/span>\n        else<\/span> high<\/span> =<\/span> mid<\/span>;<\/span>\n    }<\/span>\n\n    return<\/span> high<\/span>;<\/span>\n}<\/span>;<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>sortedIndex<\/span>(<\/span>[<\/span>10<\/span>,<\/span> 20<\/span>,<\/span> 30<\/span>,<\/span> 40<\/span>,<\/span> 50<\/span>]<\/span>,<\/span> 35<\/span>)<\/span>)<\/span> \/\/ 3<\/span><\/pre>\n<\/div>\n
\u73b0\u5728\u7684\u65b9\u6cd5\u867d\u7136\u80fd\u7528\uff0c\u4f46\u901a\u7528\u6027\u4e0d\u591f\uff0c\u6bd4\u5982\u6211\u4eec\u5e0c\u671b\u80fd\u5904\u7406\u8fd9\u6837\u7684\u60c5\u51b5\uff1a<\/p>\n
<\/p>\n
\/\/ stooges \u914d\u89d2 \u6bd4\u5982 \u4e09\u4e2a\u81ed\u76ae\u5320 The Three Stooges<\/span>\nvar<\/span> stooges<\/span> =<\/span> [<\/span>{<\/span>name<\/span>: 'stooge1'<\/span>,<\/span> age<\/span>: 10<\/span>}<\/span>,<\/span> {<\/span>name<\/span>: 'stooge2'<\/span>,<\/span> age<\/span>: 30<\/span>}<\/span>]<\/span>;<\/span>\n\nvar<\/span> result<\/span> =<\/span> sortedIndex<\/span>(<\/span>stooges<\/span>,<\/span> {<\/span>name<\/span>: 'stooge3'<\/span>,<\/span> age<\/span>: 20<\/span>}<\/span>,<\/span> function<\/span>(<\/span>stooge<\/span>)<\/span>{<\/span>\n    return<\/span> stooge<\/span>.<\/span>age<\/span>\n}<\/span>)<\/span>;<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>result<\/span>)<\/span> \/\/ 1<\/span><\/pre>\n<\/div>\n
\u6240\u4ee5\u6211\u4eec\u8fd8\u9700\u8981\u518d\u52a0\u4e0a\u4e00\u4e2a\u53c2\u6570 iteratee \u51fd\u6570\u5bf9\u6570\u7ec4\u7684\u6bcf\u4e00\u4e2a\u5143\u7d20\u8fdb\u884c\u5904\u7406\uff0c\u4e00\u822c\u8fd9\u4e2a\u65f6\u5019\uff0c\u8fd8\u4f1a\u6d89\u53ca\u5230 this \u6307\u5411\u7684\u95ee\u9898\uff0c\u6240\u4ee5\u6211\u4eec\u518d\u4f20\u4e00\u4e2a context \u6765\u8ba9\u6211\u4eec\u53ef\u4ee5\u6307\u5b9a this\uff0c\u90a3\u4e48\u8fd9\u6837\u4e00\u4e2a\u51fd\u6570\u53c8\u8be5\u5982\u4f55\u5199\u5462\uff1f<\/p>\n
<\/p>\n
\/\/ \u7b2c\u4e8c\u7248<\/span>\nfunction<\/span> cb<\/span>(<\/span>func<\/span>,<\/span> context<\/span>)<\/span> {<\/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>\n\nfunction<\/span> sortedIndex<\/span>(<\/span>array<\/span>,<\/span> obj<\/span>,<\/span> iteratee<\/span>,<\/span> context<\/span>)<\/span> {<\/span>\n\n    iteratee<\/span> =<\/span> cb<\/span>(<\/span>iteratee<\/span>,<\/span> context<\/span>)<\/span>\n\n    var<\/span> low<\/span> =<\/span> 0<\/span>,<\/span> high<\/span> =<\/span> array<\/span>.<\/span>length<\/span>;<\/span>\n    while<\/span> (<\/span>low<\/span> <<\/span> high<\/span>)<\/span> {<\/span>\n        var<\/span> mid<\/span> =<\/span> Math<\/span>.<\/span>floor<\/span>(<\/span>(<\/span>low<\/span> +<\/span> high<\/span>)<\/span> \/<\/span> 2<\/span>)<\/span>;<\/span>\n        if<\/span> (<\/span>iteratee<\/span>(<\/span>array<\/span>[<\/span>mid<\/span>]<\/span>)<\/span> <<\/span> iteratee<\/span>(<\/span>obj<\/span>)<\/span>)<\/span> low<\/span> =<\/span> mid<\/span> +<\/span> 1<\/span>;<\/span>\n        else<\/span> high<\/span> =<\/span> mid<\/span>;<\/span>\n    }<\/span>\n    return<\/span> high<\/span>;<\/span>\n}<\/span>;<\/span><\/pre>\n<\/div>\n
indexOf<\/h2>\n
sortedIndex \u4e5f\u5b8c\u6210\u4e86\uff0c\u73b0\u5728\u6211\u4eec\u5c1d\u8bd5\u7740\u53bb\u5199\u4e00\u4e2a indexOf \u548c lastIndexOf \u51fd\u6570\uff0c\u5b66\u4e60 findIndex \u548c FindLastIndex \u7684\u65b9\u5f0f\uff0c\u6211\u4eec\u5199\u4e00\u7248\uff1a<\/p>\n
<\/p>\n
\/\/ \u7b2c\u4e00\u7248<\/span>\nfunction<\/span> createIndexOfFinder<\/span>(<\/span>dir<\/span>)<\/span> {<\/span>\n    return<\/span> function<\/span>(<\/span>array<\/span>,<\/span> item<\/span>)<\/span>{<\/span>\n        var<\/span> length<\/span> =<\/span> array<\/span>.<\/span>length<\/span>;<\/span>\n        var<\/span> index<\/span> =<\/span> dir<\/span> ><\/span> 0<\/span> ? 0<\/span> : length<\/span> -<\/span> 1<\/span>;<\/span>\n        for<\/span> (<\/span>;<\/span> index<\/span> >=<\/span> 0<\/span> &&<\/span> index<\/span> <<\/span> length<\/span>;<\/span> index<\/span> +=<\/span> dir<\/span>)<\/span> {<\/span>\n            if<\/span> (<\/span>array<\/span>[<\/span>index<\/span>]<\/span> ===<\/span> item<\/span>)<\/span> return<\/span> index<\/span>;<\/span>\n        }<\/span>\n        return<\/span> -<\/span>1<\/span>;<\/span>\n    }<\/span>\n}<\/span>\n\nvar<\/span> indexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>1<\/span>)<\/span>;<\/span>\nvar<\/span> lastIndexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>-<\/span>1<\/span>)<\/span>;<\/span>\n\nvar<\/span> result<\/span> =<\/span> indexOf<\/span>(<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> 4<\/span>,<\/span> 5<\/span>]<\/span>,<\/span> 2<\/span>)<\/span>;<\/span>\n\nconsole<\/span>.<\/span>log<\/span>(<\/span>result<\/span>)<\/span> \/\/ 1<\/span><\/pre>\n<\/div>\n
fromIndex<\/h2>\n
\u4f46\u662f\u5373\u4f7f\u662f\u6570\u7ec4\u7684 indexOf \u65b9\u6cd5\u4e5f\u53ef\u4ee5\u591a\u4f20\u9012\u4e00\u4e2a\u53c2\u6570 fromIndex\uff0c\u4ece MDN \u4e2d\u770b\u5230 fromIndex \u7684\u8bb2\u7a76\u53ef\u6709\u70b9\u591a\uff1a<\/p>\n
\n
\u8bbe\u5b9a\u5f00\u59cb\u67e5\u627e\u7684\u4f4d\u7f6e\u3002\u5982\u679c\u8be5\u7d22\u5f15\u503c\u5927\u4e8e\u6216\u7b49\u4e8e\u6570\u7ec4\u957f\u5ea6\uff0c\u610f\u5473\u7740\u4e0d\u4f1a\u5728\u6570\u7ec4\u91cc\u67e5\u627e\uff0c\u8fd4\u56de -1\u3002\u5982\u679c\u53c2\u6570\u4e2d\u63d0\u4f9b\u7684\u7d22\u5f15\u503c\u662f\u4e00\u4e2a\u8d1f\u503c\uff0c\u5219\u5c06\u5176\u4f5c\u4e3a\u6570\u7ec4\u672b\u5c3e\u7684\u4e00\u4e2a\u62b5\u6d88\uff0c\u5373 -1 \u8868\u793a\u4ece\u6700\u540e\u4e00\u4e2a\u5143\u7d20\u5f00\u59cb\u67e5\u627e\uff0c-2 \u8868\u793a\u4ece\u5012\u6570\u7b2c\u4e8c\u4e2a\u5143\u7d20\u5f00\u59cb\u67e5\u627e \uff0c\u4ee5\u6b64\u7c7b\u63a8\u3002 \u6ce8\u610f\uff1a\u5982\u679c\u53c2\u6570\u4e2d\u63d0\u4f9b\u7684\u7d22\u5f15\u503c\u662f\u4e00\u4e2a\u8d1f\u503c\uff0c\u4ecd\u7136\u4ece\u524d\u5411\u540e\u67e5\u8be2\u6570\u7ec4\u3002\u5982\u679c\u62b5\u6d88\u540e\u7684\u7d22\u5f15\u503c\u4ecd\u5c0f\u4e8e 0\uff0c\u5219\u6574\u4e2a\u6570\u7ec4\u90fd\u5c06\u4f1a\u88ab\u67e5\u8be2\u3002\u5176\u9ed8\u8ba4\u503c\u4e3a 0\u3002<\/p>\n<\/blockquote>\n
\u518d\u770b\u770b lastIndexOf \u7684 fromIndex\uff1a<\/p>\n
\n
\u4ece\u6b64\u4f4d\u7f6e\u5f00\u59cb\u9006\u5411\u67e5\u627e\u3002\u9ed8\u8ba4\u4e3a\u6570\u7ec4\u7684\u957f\u5ea6\u51cf 1\uff0c\u5373\u6574\u4e2a\u6570\u7ec4\u90fd\u88ab\u67e5\u627e\u3002\u5982\u679c\u8be5\u503c\u5927\u4e8e\u6216\u7b49\u4e8e\u6570\u7ec4\u7684\u957f\u5ea6\uff0c\u5219\u6574\u4e2a\u6570\u7ec4\u4f1a\u88ab\u67e5\u627e\u3002\u5982\u679c\u4e3a\u8d1f\u503c\uff0c\u5c06\u5176\u89c6\u4e3a\u4ece\u6570\u7ec4\u672b\u5c3e\u5411\u524d\u7684\u504f\u79fb\u3002\u5373\u4f7f\u8be5\u503c\u4e3a\u8d1f\uff0c\u6570\u7ec4\u4ecd\u7136\u4f1a\u88ab\u4ece\u540e\u5411\u524d\u67e5\u627e\u3002\u5982\u679c\u8be5\u503c\u4e3a\u8d1f\u65f6\uff0c\u5176\u7edd\u5bf9\u503c\u5927\u4e8e\u6570\u7ec4\u957f\u5ea6\uff0c\u5219\u65b9\u6cd5\u8fd4\u56de -1\uff0c\u5373\u6570\u7ec4\u4e0d\u4f1a\u88ab\u67e5\u627e\u3002<\/p>\n<\/blockquote>\n
\u6309\u7167\u8fd9\u4e48\u591a\u7684\u89c4\u5219\uff0c\u6211\u4eec\u5c1d\u8bd5\u7740\u53bb\u5199\u7b2c\u4e8c\u7248\uff1a<\/p>\n
<\/p>\n
\/\/ \u7b2c\u4e8c\u7248<\/span>\nfunction<\/span> createIndexOfFinder<\/span>(<\/span>dir<\/span>)<\/span> {<\/span>\n\n    return<\/span> function<\/span>(<\/span>array<\/span>,<\/span> item<\/span>,<\/span> idx<\/span>)<\/span>{<\/span>\n        var<\/span> length<\/span> =<\/span> array<\/span>.<\/span>length<\/span>;<\/span>\n        var<\/span> i<\/span> =<\/span> 0<\/span>;<\/span>\n\n        if<\/span> (<\/span>typeof<\/span> idx<\/span> ==<\/span> \"number\"<\/span>)<\/span> {<\/span>\n            if<\/span> (<\/span>dir<\/span> ><\/span> 0<\/span>)<\/span> {<\/span>\n                i<\/span> =<\/span> idx<\/span> >=<\/span> 0<\/span> ? idx<\/span> : Math<\/span>.<\/span>max<\/span>(<\/span>length<\/span> +<\/span> idx<\/span>,<\/span> 0<\/span>)<\/span>;<\/span>\n            }<\/span>\n            else<\/span> {<\/span>\n                length<\/span> =<\/span> idx<\/span> >=<\/span> 0<\/span> ? Math<\/span>.<\/span>min<\/span>(<\/span>idx<\/span> +<\/span> 1<\/span>,<\/span> length<\/span>)<\/span> : idx<\/span> +<\/span> length<\/span> +<\/span> 1<\/span>;<\/span>\n            }<\/span>\n        }<\/span>\n\n        for<\/span> (<\/span>idx<\/span> =<\/span> dir<\/span> ><\/span> 0<\/span> ? i<\/span> : length<\/span> -<\/span> 1<\/span>;<\/span> idx<\/span> >=<\/span> 0<\/span> &&<\/span> idx<\/span> <<\/span> length<\/span>;<\/span> idx<\/span> +=<\/span> dir<\/span>)<\/span> {<\/span>\n            if<\/span> (<\/span>array<\/span>[<\/span>idx<\/span>]<\/span> ===<\/span> item<\/span>)<\/span> return<\/span> idx<\/span>;<\/span>\n        }<\/span>\n        return<\/span> -<\/span>1<\/span>;<\/span>\n    }<\/span>\n}<\/span>\n\nvar<\/span> indexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>1<\/span>)<\/span>;<\/span>\nvar<\/span> lastIndexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>-<\/span>1<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u4f18\u5316<\/h2>\n
\u5230\u6b64\u4e3a\u6b62\uff0c\u5df2\u7ecf\u5f88\u63a5\u8fd1\u539f\u751f\u7684 indexOf \u51fd\u6570\u4e86\uff0c\u4f46\u662f underscore \u5728\u6b64\u57fa\u7840\u4e0a\u8fd8\u505a\u4e86\u4e24\u70b9\u4f18\u5316\u3002<\/p>\n
\u7b2c\u4e00\u4e2a\u4f18\u5316\u662f\u652f\u6301\u67e5\u627e NaN\u3002<\/p>\n
\u56e0\u4e3a NaN \u4e0d\u5168\u7b49\u4e8e NaN\uff0c\u6240\u4ee5\u539f\u751f\u7684 indexOf \u5e76\u4e0d\u80fd\u627e\u51fa NaN \u7684\u4e0b\u6807\u3002<\/p>\n
\n
[<\/span>1<\/span>,<\/span> NaN<\/span>]<\/span>.<\/span>indexOf<\/span>(<\/span>NaN<\/span>)<\/span> \/\/ -1<\/span><\/pre>\n<\/div>\n
\u90a3\u4e48\u6211\u4eec\u8be5\u5982\u4f55\u5b9e\u73b0\u8fd9\u4e2a\u529f\u80fd\u5462\uff1f<\/p>\n
\u5c31\u662f\u4ece\u6570\u7ec4\u4e2d\u627e\u5230\u7b26\u5408\u6761\u4ef6\u7684\u503c\u7684\u4e0b\u6807\u561b\uff0c\u4e0d\u5c31\u662f\u6211\u4eec\u6700\u4e00\u5f00\u59cb\u5199\u7684 findIndex \u5417\uff1f<\/p>\n
\u6211\u4eec\u6765\u5199\u4e00\u4e0b\uff1a<\/p>\n
<\/p>\n
\/\/ \u7b2c\u4e09\u7248<\/span>\nfunction<\/span> createIndexOfFinder<\/span>(<\/span>dir<\/span>,<\/span> predicate<\/span>)<\/span> {<\/span>\n\n    return<\/span> function<\/span>(<\/span>array<\/span>,<\/span> item<\/span>,<\/span> idx<\/span>)<\/span>{<\/span>\n\n        if<\/span> (<\/span>)<\/span> {<\/span> ... }<\/span>\n\n        \/\/ \u5224\u65ad\u5143\u7d20\u662f\u5426\u662f NaN<\/span>\n        if<\/span> (<\/span>item<\/span> !==<\/span> item<\/span>)<\/span> {<\/span>\n            \/\/ \u5728\u622a\u53d6\u597d\u7684\u6570\u7ec4\u4e2d\u67e5\u627e\u7b2c\u4e00\u4e2a\u6ee1\u8db3isNaN\u51fd\u6570\u7684\u5143\u7d20\u7684\u4e0b\u6807<\/span>\n            idx<\/span> =<\/span> predicate<\/span>(<\/span>array<\/span>.<\/span>slice<\/span>(<\/span>i<\/span>,<\/span> length<\/span>)<\/span>,<\/span> isNaN<\/span>)<\/span>\n            return<\/span> idx<\/span> >=<\/span> 0<\/span> ? idx<\/span> +<\/span> i<\/span>: -<\/span>1<\/span>;<\/span>\n        }<\/span>\n\n        for<\/span> (<\/span>)<\/span> {<\/span> ... }<\/span>\n    }<\/span>\n}<\/span>\n\nvar<\/span> indexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>1<\/span>,<\/span> findIndex<\/span>)<\/span>;<\/span>\nvar<\/span> lastIndexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>-<\/span>1<\/span>,<\/span> findLastIndex<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u7b2c\u4e8c\u4e2a\u4f18\u5316\u662f\u652f\u6301\u5bf9\u6709\u5e8f\u7684\u6570\u7ec4\u8fdb\u884c\u66f4\u5feb\u7684\u4e8c\u5206\u67e5\u627e\u3002<\/p>\n
\u5982\u679c indexOf \u7b2c\u4e09\u4e2a\u53c2\u6570\u4e0d\u4f20\u5f00\u59cb\u641c\u7d22\u7684\u4e0b\u6807\u503c\uff0c\u800c\u662f\u4e00\u4e2a\u5e03\u5c14\u503c true\uff0c\u5c31\u8ba4\u4e3a\u6570\u7ec4\u662f\u4e00\u4e2a\u6392\u597d\u5e8f\u7684\u6570\u7ec4\uff0c\u8fd9\u65f6\u5019\uff0c\u5c31\u4f1a\u91c7\u7528\u66f4\u5feb\u7684\u4e8c\u5206\u6cd5\u8fdb\u884c\u67e5\u627e\uff0c\u8fd9\u4e2a\u65f6\u5019\uff0c\u53ef\u4ee5\u5229\u7528\u6211\u4eec\u5199\u7684 sortedIndex \u51fd\u6570\u3002<\/p>\n
\u5728\u8fd9\u91cc\u76f4\u63a5\u7ed9\u6700\u7ec8\u7684\u6e90\u7801\uff1a<\/p>\n
<\/p>\n
\/\/ \u7b2c\u56db\u7248<\/span>\nfunction<\/span> createIndexOfFinder<\/span>(<\/span>dir<\/span>,<\/span> predicate<\/span>,<\/span> sortedIndex<\/span>)<\/span> {<\/span>\n\n    return<\/span> function<\/span>(<\/span>array<\/span>,<\/span> item<\/span>,<\/span> idx<\/span>)<\/span>{<\/span>\n        var<\/span> length<\/span> =<\/span> array<\/span>.<\/span>length<\/span>;<\/span>\n        var<\/span> i<\/span> =<\/span> 0<\/span>;<\/span>\n\n        if<\/span> (<\/span>typeof<\/span> idx<\/span> ==<\/span> \"number\"<\/span>)<\/span> {<\/span>\n            if<\/span> (<\/span>dir<\/span> ><\/span> 0<\/span>)<\/span> {<\/span>\n                i<\/span> =<\/span> idx<\/span> >=<\/span> 0<\/span> ? idx<\/span> : Math<\/span>.<\/span>max<\/span>(<\/span>length<\/span> +<\/span> idx<\/span>,<\/span> 0<\/span>)<\/span>;<\/span>\n            }<\/span>\n            else<\/span> {<\/span>\n                length<\/span> =<\/span> idx<\/span> >=<\/span> 0<\/span> ? Math<\/span>.<\/span>min<\/span>(<\/span>idx<\/span> +<\/span> 1<\/span>,<\/span> length<\/span>)<\/span> : idx<\/span> +<\/span> length<\/span> +<\/span> 1<\/span>;<\/span>\n            }<\/span>\n        }<\/span>\n        else<\/span> if<\/span> (<\/span>sortedIndex<\/span> &&<\/span> idx<\/span> &&<\/span> length<\/span>)<\/span> {<\/span>\n            idx<\/span> =<\/span> sortedIndex<\/span>(<\/span>array<\/span>,<\/span> item<\/span>)<\/span>;<\/span>\n            \/\/ \u5982\u679c\u8be5\u63d2\u5165\u7684\u4f4d\u7f6e\u7684\u503c\u6b63\u597d\u7b49\u4e8e\u5143\u7d20\u7684\u503c\uff0c\u8bf4\u660e\u662f\u7b2c\u4e00\u4e2a\u7b26\u5408\u8981\u6c42\u7684\u503c<\/span>\n            return<\/span> array<\/span>[<\/span>idx<\/span>]<\/span> ===<\/span> item<\/span> ? idx<\/span> : -<\/span>1<\/span>;<\/span>\n        }<\/span>\n\n        \/\/ \u5224\u65ad\u662f\u5426\u662f NaN<\/span>\n        if<\/span> (<\/span>item<\/span> !==<\/span> item<\/span>)<\/span> {<\/span>\n            idx<\/span> =<\/span> predicate<\/span>(<\/span>array<\/span>.<\/span>slice<\/span>(<\/span>i<\/span>,<\/span> length<\/span>)<\/span>,<\/span> isNaN<\/span>)<\/span>\n            return<\/span> idx<\/span> >=<\/span> 0<\/span> ? idx<\/span> +<\/span> i<\/span>: -<\/span>1<\/span>;<\/span>\n        }<\/span>\n\n        for<\/span> (<\/span>idx<\/span> =<\/span> dir<\/span> ><\/span> 0<\/span> ? i<\/span> : length<\/span> -<\/span> 1<\/span>;<\/span> idx<\/span> >=<\/span> 0<\/span> &&<\/span> idx<\/span> <<\/span> length<\/span>;<\/span> idx<\/span> +=<\/span> dir<\/span>)<\/span> {<\/span>\n            if<\/span> (<\/span>array<\/span>[<\/span>idx<\/span>]<\/span> ===<\/span> item<\/span>)<\/span> return<\/span> idx<\/span>;<\/span>\n        }<\/span>\n        return<\/span> -<\/span>1<\/span>;<\/span>\n    }<\/span>\n}<\/span>\n\nvar<\/span> indexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>1<\/span>,<\/span> findIndex<\/span>,<\/span> sortedIndex<\/span>)<\/span>;<\/span>\nvar<\/span> lastIndexOf<\/span> =<\/span> createIndexOfFinder<\/span>(<\/span>-<\/span>1<\/span>,<\/span> findLastIndex<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff1a\u5728 underscore \u7684\u5b9e\u73b0\u4e2d\uff0c\u53ea\u6709 indexOf \u662f\u652f\u6301\u6709\u5e8f\u6570\u7ec4\u4f7f\u7528\u4e8c\u5206\u67e5\u627e\uff0clastIndexOf \u5e76\u4e0d\u652f\u6301\u3002<\/p>\n<\/td>\n
\u6587\u7ae0\u8f6c\u8f7d\u81eahttps:\/\/github.com\/mqyqingfeng\/Blog\/issues\/37<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
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 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-1374","post","type-post","status-publish","format-standard","hentry","category-learn"],"_links":{"self":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1374"}],"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=1374"}],"version-history":[{"count":1,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1374\/revisions"}],"predecessor-version":[{"id":1467,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1374\/revisions\/1467"}],"wp:attachment":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1374"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1374"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1374"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}