Finding a Key's Value from an object within an array - Javascript

Question

I have tried many things to get this working correctly but I can't

Here is my problem:

I have an array of objects in javascript which looks something like this:

var myArrOfObjs = [];
var myObject1 = {};
myObject1.key = '1234';
myObject1.label = 'Richard Clifford';

myArrOfObjs.push( myObject1 );

and I need to do something like:

if( !containsObject( myObject1, myArrOfOjbs ) ){
    // Do stuff
}

I need the containsObject function to check for key values within the found object (if any), so if containsObject( myObject1, myArrOfOjbs ) finds the object, I need to check to see if the key of that is the same as the one I am currently trying to push.

The reason I need it to check the keys is because I have tried this function which I found else where on StackOverflow, but it isn't quite working.

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

    return false;
}

It still pushes the object to the array even when it already contains the object.

Please let me know if you need anything clearing up, I realise that it isn't the easiest post to read/understand.

Thanks!

This containsObject method should work. There is probably a problem with the calling code. Could you show it (make an autonomous reduced code displaying the problem if possible) ? — Denys Séguret
– Denys Séguret, Commented Mar 14, 2012 at 13:36

Mark Byers · Accepted Answer · 2012-03-14 13:35:45Z

3

You need to change the equality test to compare the keys:

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

    return false;
}

answered Mar 14, 2012 at 13:35

Mark Byers

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1 Comment

DarkMantis Over a year ago

That worked perfectly. Shows how little I know about javascript. I've only just start learning it. So thanks a lot! much appreciated!

GNi33 · Accepted Answer · 2012-03-14 13:50:31Z

1

I have got this function that gets added to the prototype-chain of the Array-Object, so you can just call list.hasObject(obj).

Array.prototype.hasObject = (
  !Array.indexOf ? function (o)
  {
    var l = this.length + 1;
    while (l -= 1)
    {
        if (this[l - 1] === o)
        {
            return true;
        }
    }
    return false;
  } : function (o)
  {
    return (this.indexOf(o) !== -1);
  }
);

small fiddle for this: http://jsfiddle.net/NE9kx/

edited Mar 14, 2012 at 13:50

answered Mar 14, 2012 at 13:43

GNi33

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1 Comment

DarkMantis Over a year ago

Good answer, but I have gone with the above one. Thanks anyway!

ZER0 · Accepted Answer · 2012-03-14 13:51:29Z

1

Maybe it's not the answer you're looking for, but I wonder why don't use an Object instead of an Array, if you have a key:

var objectList = {};

var myObject { key : '1234', label : 'Richard Clifford' };

objectList[myObject.key] = myObject;

So if you want to iterate:

for (var key in objectList) {
    if (objectList.hasOwnProperty(key)
        alert(key);
}

If you want to access to the object with a key given you have just to:

alert(objectList['1234'].label);

answered Mar 14, 2012 at 13:51

ZER0

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1 Comment

DarkMantis Over a year ago

The reason why is due to the third-party software which I am writing an extension for, it uses an array of objects. Thanks for the suggestion for future reference I will use objects :)

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