Select array index by object value

Question

If I have an array like this:

var array = [{ID:1,value:'test1'},
             {ID:3,value:'test3'},
             {ID:2,value:'test2'}]

I want to select an index by the ID.

i.e, I want to somehow select ID:3, and get {ID:3,value:'test3'}.

What is the fastest and most lightweight way to do this?

possible duplicate of [Find object by id in array of javascript objects](http://stackoverflow.com/questions/7364150/find-object-by-id-in-array-of-javascript-objects) — Felix Kling, Apr 10 '14 at 23:24

score 5 · Accepted Answer · answered Apr 10 '14 at 22:57

Use array.filter:

var results = array.filter(function(x) { return x.ID == 3 });

It returns an array, so to get the object itself, you'd need [0] (if you're sure the object exists):

var result = array.filter(function(x) { return x.ID == 3 })[0];

Or else some kind of helper function:

function getById(id) {
    var results = array.filter(function(x) { return x.ID == id });
    return (results.length > 0 ? results[0] : null);
}
var result = getById(3);

score 0 · Answer 2 · answered Apr 10 '14 at 22:58

0

With lodash you can use find with pluck-style input:

_.find(result, {ID: 3})

answered Apr 10 '14 at 22:58

djechlin

59,258
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nachoalvarez · Answer 3 · 2014-04-10T23:18:35.317

0

I would go for something like this:

function arrayObjectIndexOf(myArray, property, searchTerm) {
    for (var i = 0, len = myArray.length; i < len; i++) {
        if (myArray[i].property === searchTerm)
            return myArray[i];
    }
    return -1;
}

In your case you should do:

arrayObjectIndexOf(array, id, 3);

edited Apr 10 '14 at 23:18

answered Apr 10 '14 at 23:12

nachoalvarez

31
3

score 0 · Answer 4 · answered Apr 10 '14 at 23:15

Using filter is not the fastest way because filter will always iterate through the entire array even if element being search for is the first element. This can perform poorly on larger arrays.

If you are looking for fastest way, simply looping through until the element is found might be best option. Something like below.

var findElement = function (array, inputId) {
    for (var i = array.length - 1; i >= 0; i--) {
        if (array[i].ID === inputId) {
            return array[i];
        }
    }
};

findElement(array, 3);

@nachoalvarez, your code would run into errors. You should use [property] instead of .property — Ashutosh Upadhyay, Apr 10 '14 at 23:17

score 0 · Answer 5 · answered Apr 18 '15 at 21:01

0

var indexBy = function(array, property) {
  var results = {};
  (array||[]).forEach(function(object) {
    results[object[property]] = object;
  });
  return results
};

which lets you var indexed = indexBy(array, "ID");

answered Apr 18 '15 at 21:01

Blair Anderson

19,463
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Select array index by object value

5 Answers5