Assigning a javascript object with and object inside an array

Question

I am just curious about this.

Let's say I have an array of objects and I create 1 object, lets name the array of objects items and the object item.

I want to get a particular item in my array of items by using the following code:

//gets an item base on ID
function get_item(td){
    var item = undefined;
    $.each(items, function(i, val) {
        if(val.item_id == td){
            item = val;
        }   
    });
    return item;
}

The get_item() basically gets an object matched with the supplied id.

So my question is this. What if I changed the properties of item will it also changed the properties of an object associated with it within the array?

Thank you very much!

show more code. Right after your "let's say I have...", show the code that you think corresponds to that situation. — Mike 'Pomax' Kamermans
– Mike 'Pomax' Kamermans, Commented Jun 1, 2015 at 4:23
if you are changing in item with reference to the array then the item will change. — Ruchan
– Ruchan, Commented Jun 1, 2015 at 4:25
If you are returning the same instance as stored in the array... yes it will — Arun P Johny
– Arun P Johny, Commented Jun 1, 2015 at 4:25

Felix Kling · Accepted Answer · 2015-06-01 04:26:09Z

6

What if I changed the properties of item will it also changed the properties of an object associated with it within the array?

Yes.

Objects are not copied. Instead, references to the objects are passed around. Simplest example:

var a = [];
var b = a;
b.push(1);
console.log(a); // logs [1]

Many object-oriented programming languages work like this.

answered Jun 1, 2015 at 4:26

Felix Kling

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Comments

gabo · Accepted Answer · 2015-06-01 04:39:42Z

2

The value of the object inside the array will also change because it's a reference. If you want more information I highly recommend reading Objects and Prototypes.

If you don't want it to change then you should use something like lodash's _.clone() function.

Also you could use filter to get the object:

function get_item(td){
    return items.filter(function(item) {
        return item.id === td;
    })[0];
}

edited Jun 1, 2015 at 4:39

answered Jun 1, 2015 at 4:29

gabo

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Comments

PhuLuong · Accepted Answer · 2015-06-01 04:33:41Z

1

You can update you function to:

var data= array();
function get_item(propertyValue, propertyName){
    var retval;
    for(var i = 0; i < data.length; i++){
         if(data[i][propertyName]==propertyValue){
            retval = data[i];
            break;
         }
    }
    return retval;
}

Use it

var item1 = get_item(1,"id");
var item2 = get_item("john","name");

edited Jun 1, 2015 at 4:33

answered Jun 1, 2015 at 4:27

PhuLuong

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4 Comments

iamjc015 Over a year ago

can you please elaborate more?

Felix Kling Over a year ago

How does this answer the OP's question? "What if I changed the properties of item will it also changed the properties of an object associated with it within the array?"

iamjc015 Over a year ago

It does not answer, but it helps.

Felix Kling Over a year ago

@JCFrane: There are many things that help. That doesn't mean that it is appropriate to post about them. As the term already implies, "answers" should answer the question that was posed. As the term implies, "answers" should answer the question that was posed.

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