获取过滤值的对象键 [英] Get object keys for filtered values

问题描述

案例很简单 - 我有以下对象:

The case is simple - I've got a following object:

Object {1: false, 2: true, 3: false, 4: false, 5: false, 6: false, 7: false, 8: true, 12: false, 13: false, 14: false, 15: false, 16: false, 17: false, 18: false, 19: false} 

并且我需要使用下划线获取具有真值的 id 数组.在上述情况下，将是:

and I need to get an array of ids that had true value, using underscore. In above case that would be:

[2, 8]

我尝试了一些东西，但我有点卡住了.有人知道吗?

I tried few things but I'm a bit stuck. Does anyone have any idea?

推荐答案

var keys = [];
_.each( obj, function( val, key ) {
  if ( val ) {
    keys.push(key);
  }
});

使用普通下划线可能有更简单/更短的方法.

如果这里有人使用 Lodash 而不是 Underscore，以下也是可能的，很短并且易于阅读:

In case anyone here uses Lodash instead of Underscore, the following is also possible, which is very short and easy to read:

var keys = _.invert(obj, true)[ "true" ];

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