Pushing a multidimensional array in javascript

Question

Please check down the code below, I want to push an object multiple times into an array and set a specified path. Hope someone can help. TNX!

To keep it simple I just removed all loops and static addressed my array, but still no success and I don't got any idea why:

wrong result:

let myObject = {
"version": "2.0",
"worker": {
    "todo": []
 }
};
let myObjectArray = new Array();
myObjectArray.push(myObject);
myObjectArray.push(myObject);
myObjectArray[0]["worker"]["todo"] = "test";
console.log(myObjectArray);

-> wrong output array

correct result:

let myObjectArray = [
{
    "version": "2.0",
    "worker": {
        "todo": []
    }
},
{
    "version": "2.0",
    "worker": {
        "todo": []
    }
}
];
myObjectArray[0]["worker"]["todo"] = "test";
console.log(myObjectArray);

-> correct output array

Karthik RP · Accepted Answer · 2017-12-04 08:32:21Z

2

If you want to push duplicate items then you need to push different instances of object instead of pushing the object reference.

Just check the below solution, it should be working as desired.

let myObject = {
"version": "2.0",
"worker": {
    "todo": []
 }
};
let myObjectArray = new Array();
myObjectArray.push(JSON.parse(JSON.stringify(myObject)));
myObjectArray.push(JSON.parse(JSON.stringify(myObject)));
myObjectArray[0]["worker"]["todo"] = "test";
console.log(myObjectArray);

edited Dec 4, 2017 at 8:32

answered Dec 4, 2017 at 8:14

Karthik RP

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2 Comments

Mihai Alexandru-Ionut Over a year ago

What it's happened if you have objects which contains functions ?

Karthik RP Over a year ago

@Alexandru-IonutMihai We can't do that, because function scopes cannot be copied. You can get more detailed answer over here, stackoverflow.com/a/18089155/5367148

Shuja Ahmed · Accepted Answer · 2017-12-04 08:19:24Z

0

You have to use the deep copying here to make sure the 2 objects are treated as separate instance instead of being the references to the same object.

For "deep" copy, use JSON.parse(JSON.stringify(myObject)) so it will look something like:

myObjectArray.push(JSON.parse(JSON.stringify(myObject)));

answered Dec 4, 2017 at 8:19

Shuja Ahmed

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Comments

SPlatten · Accepted Answer · 2017-12-04 08:13:23Z

0

The first example, pushes the same object into the array, so you will have a duplicate of the same object in the array, modifying the first instance will also effect the 2nd instance.

In your second example you are creating two separate objects in the array, modifying the first element has no effect on the second.

Objects are always treated as references in JavaScript.

answered Dec 4, 2017 at 8:13

SPlatten

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