best way to get a specific object from and array without looping

Question

In one of the controllers of my angular application i have a variable set as follows.

SomeService.get({}, function(data){
    // this sets xyz as the list of the data retrieved 
    // from the resource within the controllers scope
    $scope.xyz = data.objects;    
});

Now $scope.xyz looks something like

[
    0: {id: 1, ...more data here ...},
    1: {id: 2, ...more data here ...},
    2: {id: 3, ...more data here ...},
    3: {id: 4, ...more data here ...},
    4: {id: 5, ...more data here ...},
    5: {id: 6, ...more data here ...},
]

What i am trying to do is get an object within xyz using the id property (not the list index). I am aware that I can iterate over the array as follows.

angular.forEach($scope.xyz, function(obj){ return obj.id == 1;});

but is there a way I can do it without looping over the list ?

Are you trying to go without underscore/lo-dash or similar utility belts? — Stewie, Mar 14 '13 at 14:24
@Stewie well I am open to options, but it would be good if there is a way without depending on a lib for such a small use case. — Amyth, Mar 15 '13 at 09:07
Well, Angular does not try to offer such low-level utilities, so this question is all about JavaScript solution for loop-less mapping. For that matter I'd say @Bergi answer is the best you can expect. — Stewie, Mar 15 '13 at 09:44
Check the answer to [this question.](http://stackoverflow.com/questions/7364150/find-object-by-id-in-array-of-javascript-objects) The recommendation is to use the jQuery [grep](http://api.jquery.com/jQuery.grep/) function. — ckersch, Mar 14 '13 at 14:02

score 8 · Answer 1 · edited Mar 25 '16 at 11:57

8

Though this is already answered a year ago, since this is one of the top results in Google, I thought I can add the following suggestion which may be the easiest way to filter. After injecting $filter into your controller,

var result = $filter('filter')($scope.xyz, {id:"1"});

reference: https://docs.angularjs.org/api/ng/filter/filter

edited Mar 25 '16 at 11:57

Volkan Paksoy

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answered Oct 15 '14 at 20:57

Kay Gee

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score 5 · Accepted Answer · answered Mar 14 '13 at 14:10

No, you can't really avoid looping (O(n)) unless there are some preconditions met.

If the array is sorted by id, you can use a binary search algorithm (O(log n)).
If the array index always corresponds to the id-1 (or some similar simple formula), you can directly access it in O(1).

If those conditions are not fulfilled initially, but you need to access the items by id multiple times, it could be helpful to bring them in that form (sorting/building a hash map).

best way to get a specific object from and array without looping

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