how to check a literal object is in an Javascript array

Question

I have an array & a literal object like this

var arr = [{a: 1}, {a: 2}, {a: 3}];
var e1 = {a: 1};

I want to implement a function (ex: containsObject(e1, arr)) what should return true in this case.

Please teach me the way without overriding base classes like Array.prototype.indexof

containsObject should be implemented in such a way that you also pass key to be tested in base-array — Rayon
– Rayon, Commented Apr 27, 2016 at 11:42
Related: How to determine equality for two JavaScript objects? — Felix Kling
– Felix Kling, Commented Apr 27, 2016 at 11:58

jcubic · Accepted Answer · 2016-04-27 11:52:51Z

2

Try this:

var arr = [{a: 1}, {a: 2}, {a: 3}];
var e1 = {a: 1};
for (var i=0; i<arr.length; i++) {
  var found = true;
  for (var key in e1) {
    if (e1[key] != arr[i][key]) {
      found = false;
      break;
    }
  }
  if (found) {
    alert('found at index ' + i);
    break;
  }
}

answered Apr 27, 2016 at 11:52

jcubic

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Comments

Ma Yubo · Accepted Answer · 2016-04-27 12:19:34Z

2

        var arr = [{a: 1}, {a: 2}, {a: 3}];
var e1 = {a: 1};
function containsObject(e1, arr) {
    var i;
    for (i = 0; i < arr.length; i++) {
        if (JSON.stringify(arr[i]) === JSON.stringify(e1)) {
            alert("we found it")
        }else{
            alert(JSON.stringify(e1)+"not equal to"+JSON.stringify(arr[i]))
        }
    }
}
containsObject(e1, arr)

if you don't mind compare them in string, use this way. JSON.stringify() convert object to json string, I think you expect compare them in human vision, then that is it.

I don't think the 2 different object can be compared.they are 2 instance from Object,

edited Apr 27, 2016 at 12:19

answered Apr 27, 2016 at 12:05

Ma Yubo

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3 Comments

Vu Le Anh Over a year ago

Thank Ma Yubo. We save a loop, but I can trust function JSON.stringify. Is there any case what will be wrong with JSON.stringify?

Ma Yubo Over a year ago

don't know yet, JSON.stringify should be able to use for any object

Vu Le Anh Over a year ago

yes, I know function JSON.stringify. I just consider in what case, this way is wrong (not find yet). I prefer your way and use it, the jcubic's way is right. I thought about it, but I am afraid of 2 loop :) Thank again

Roli Agrawal · Accepted Answer · 2016-04-27 12:33:02Z

0

This may Help you

function containsObject(e1, arr)
    {
      var k=false;
      ap=arr.filter(function(a){
      if(JSON.stringify(a) === JSON.stringify(e1))
      {k=true; 
       return(true);}
     });
    (k===true)?console.log("in array"):console.log("not in array");
    }
var arr = [{a: 1}, {a: 2}, {a: 3}];
var e1 = {a: 1};
containsObject(e1,arr);

Since array is not containing any method so we can use stringify to compare objects.

answered Apr 27, 2016 at 12:33

Roli Agrawal

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Comments

Deepak Mani · Accepted Answer · 2016-04-27 11:44:33Z

-2

This may help you.

function containsObject(e1, arr) {
    var i;
    for (i = 0; i < arr.length; i++) {
        if (arr[i] === e1) {
            return true;
        }
    }

    return false;
}

answered Apr 27, 2016 at 11:44

Deepak Mani

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1 Comment

Vu Le Anh Over a year ago

you cannot compare 2 literal object by operator ===

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