javascript - 根据内容提取对象数组

Question

在 JavaScript 中，我有一个像这样的 JSON 数组:

var r = [{"name":"a","bool":false},{"name":"b","bool":false},
         {"name":"c","bool":false},{"name":"a","bool":false},
         {"name":"b","bool":false},{"name":"c","bool":true},
         {"name":"a","bool":true}];

我想构建另一个数组，其中包含 name=="a"和 bool==false 的所有对象。我通过循环解决了这个问题，但我想知道是否还有其他方法可以做到这一点。

我该怎么办？

[编辑]我的循环是:

var rLen = r.length;
var newArray = [];

for(var i=0;i<rLen;i++) {
    if(r[i].name=="a"&&r[i].bool==false) {
        newArray.push(r[i]);
    }
}

Answer 1

最后总会通过内部循环来解决，例如

var r = [{"name":"a","bool":false},{"name":"b","bool":false},
         {"name":"c","bool":false},{"name":"a","bool":false},
         {"name":"b","bool":false},{"name":"c","bool":true},
         {"name":"a","bool":true}];

var result = r.filter(function(item){
    return item.name === 'a' && !item.bool;
});

如果您查看 polyfill，您会注意到循环:

if (!Array.prototype.filter) {
  Array.prototype.filter = function(fun/*, thisArg*/) {
    'use strict';

    if (this === void 0 || this === null) {
      throw new TypeError();
    }

    var t = Object(this);
    var len = t.length >>> 0;
    if (typeof fun !== 'function') {
      throw new TypeError();
    }

    var res = [];
    var thisArg = arguments.length >= 2 ? arguments[1] : void 0;
    for (var i = 0; i < len; i++) { // <-- 
      if (i in t) {
        var val = t[i];

        // NOTE: Technically this should Object.defineProperty at
        //       the next index, as push can be affected by
        //       properties on Object.prototype and Array.prototype.
        //       But that method's new, and collisions should be
        //       rare, so use the more-compatible alternative.
        if (fun.call(thisArg, val, i, t)) {
          res.push(val);
        }
      }
    }

    return res;
  };
}

既然您对性能感兴趣，这里有一个比较两者的 jsperf:http://jsperf.com/aarontgrogg-array-filter-vs-for-loop