javascript 获取过滤值的对象键

Get object keys for filtered values

提问by ducin

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

案例很简单 - 我有以下对象：

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} 

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

并且我需要使用下划线获取具有真实值的 id 数组。在上述情况下，将是：

[2, 8]

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

我尝试了几件事，但我有点卡住了。有谁有想法吗？

回答by gustavohenke

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

There may be easier/shorter ways using plain Underscore.

使用普通的 Underscore 可能有更简单/更短的方法。

---

---

In case anyone here uses Lodashinstead of Underscore, the following is also possible, which is very shortand easy to read:

如果这里有人使用Lodash而不是Underscore，以下也是可能的，它非常简短且易于阅读：

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

回答by Cláudio Silva

Giorgi Kandelaki gave a good answer, but it had some potential problems (see my comment on his answer).

Giorgi Kandelaki 给出了一个很好的答案，但它有一些潜在的问题（见我对他的回答的评论）。

The correct way is:

正确的方法是：

_(obj).pairs().filter(_.last).map(_.first)

or

或者

_.map(_.filter(_.pairs(obj),_.last),_.first)

回答by Dmitri Algazin

var data = {1: false, 2: true, 3: false, 4: true};

var filteredIds = _.filter(_.keys(data), function (key) {
    return data[key];
});

// result [2, 4]


var rejectedIds = _.reject(_.keys(data), function (key) {
    return data[key];
});

// result [1, 3]

回答by P?l

You can use _.pick. Like this:

您可以使用_.pick. 像这样：

var data = {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}

var keys = _.keys(_.pick(data, function(value) {
  return value;
}));

回答by Voxel

var obj = {1: false, 2: true /*...*/};

you can use reduce:

你可以使用减少：

_(obj).reduce(function(memo, val, key){
    if (val)
        memo.push(key);
    return memo;
}, []);

or chain map:

或链图：

_(obj).chain().map(function(val, key){
    if (val)
        return key;
}).reject(_.isUndefined).value();

回答by Giorgi Kandelaki

You can try this:

你可以试试这个：

_.pairs(obj)
 .filter(function(pair) { return pair[1] })
 .map(function(pair) { return pair[0] })

Or the same but bit more concise:

或相同但更简洁：

_.pairs(obj).filter(_.last).map(_.first)

回答by gentiane

You can do it very easily

你可以很容易地做到

var obj = { a: false, b: false, c: true, d: false, e: true, f: false };
    name, names;

name = _.findKey(obj, true);
// -> 'c'
names = _.findKeys(obj, true);
// -> ['c', 'e']

For that you juste need to extend underscore a little :

为此，您需要稍微扩展下划线：

_.mixin({

  findKey: function(obj, search, context) {
    var result,
        isFunction = _.isFunction(search);

    _.any(obj, function (value, key) {
      var match = isFunction ? search.call(context, value, key, obj) : (value === search);
      if (match) {
        result = key;
        return true;
      }
    });

    return result;
  },

  findKeys: function(obj, search, context) {
    var result = [],
        isFunction = _.isFunction(search);

    _.each(obj, function (value, key) {
      var match = isFunction ? search.call(context, value, key, obj) : (value === search);
      if (match) {
        result.push(key);
      }
    });

    return result;
  }
});

And you can even use a function as filter, like this :

您甚至可以使用函数作为过滤器，如下所示：

var team = {
  place1: { name: 'john', age: 15 },
  place2: { name: 'tim', age: 21 },
  place3: { name: 'jamie', age: 31 },
  place4: { name: 'dave', age: 17 }}

// Determine the places of players who are major
var placeNames = _.findKeys(team, function(value) { return value.age >= 18; });
// -> ['place2', 'place3']

Enjoy ;-)

享受 ;-）

回答by sprynk

My version:

我的版本：

var list = {
    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
};

_.chain(list).map(function(val, key) {
    return val ? parseInt(key) : undefined
}).reject(function(val) {
    return _.isUndefined(val);
}).value();
// returns [2,8]

回答by emil

This might be easier

这可能更容易

result = _.chain(obj)
    .map(function(value, key){
        return value?key:false;
    })
    .filter(function(v){
        return v
    })
    .value();

回答by Manu

I use this one: Retrieve all keys with the same value from an object (not only an object with just boolean values) using lodash

我使用这个： 使用lodash

function allKeys(obj, value) {
  _.keys(_.pick(obj, function (v, k) { return v === value; }));
}

Example:

例子：

var o = {a: 3, b: 5, c: 3};
var desiredKeys = allKeys(o, 3);
// => [a, c]