How to Retrieve a Value Associated with a Key in a JavaScript Array of Objects

Question

How to Retrieve a Value Associated with a Key in a JavaScript Array of Objects

I've exhausted multiple attempts to solve this issue, but unfortunately, I can't seem to get it right.

Here's the problem at hand:

In my JavaScript code, I have an array of objects structured like this:

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

myArrOfObjs.push( myObject1 );

Now, what I'm trying to achieve is something along these lines:

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

The containsObject function needs to verify the key values within the object it finds. So, when

containsObject( myObject1, myArrOfOjbs )

locates the object, it should check if the key matches the one we're currently attempting to push.

I require this key-check functionality because I experimented with a similar function that I discovered on StackOverflow, but it isn't functioning as expected.

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

    return false;
}

Even with this function in place, the object still gets added to the array even if it's already present.

If there's any confusion or ambiguity in my explanation, please don't hesitate to ask for clarification. I understand that my post may not be the easiest to comprehend.

Thank you!

javascript arrays object loops

Answer 1

Answer №1

To effectively find the matching keys, ensure you modify the equality test:

function checkForObjectEquality(object, list) {
    var index;
    for (index = 0; index < list.length; index++) {
        if (list[index].key === object.key) {
            return true;
        }
    }

    return false;
}

Answer 2

To effectively find the matching keys, ensure you modify the equality test:

function checkForObjectEquality(object, list) {
    var index;
    for (index = 0; index < list.length; index++) {
        if (list[index].key === object.key) {
            return true;
        }
    }

    return false;
}

Answer 3

Answer №2

A custom function has been implemented that is added to the prototype-chain of the Array Object. This allows you to easily check if an object exists in the array by calling 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);
  }
);

Check out a live example here: http://jsfiddle.net/NE9kx/

Answer 4

A custom function has been implemented that is added to the prototype-chain of the Array Object. This allows you to easily check if an object exists in the array by calling 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);
  }
);

Check out a live example here: http://jsfiddle.net/NE9kx/

Answer 5

Answer №3

Perhaps this approach may not align with your initial expectations, but have you considered using an Object instead of an Array, especially when dealing with a key-value pair?

var myObject = {};

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

myObject[objData.key] = objData;

When it comes to iteration, you can simply loop through the object like this:

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

If you need to retrieve an object using a specific key, you can do so easily:

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

Answer 6

Perhaps this approach may not align with your initial expectations, but have you considered using an Object instead of an Array, especially when dealing with a key-value pair?

var myObject = {};

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

myObject[objData.key] = objData;

When it comes to iteration, you can simply loop through the object like this:

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

If you need to retrieve an object using a specific key, you can do so easily:

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

How to Retrieve a Value Associated with a Key in a JavaScript Array of Objects

Answer №1

Answer №2

Answer №3

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