Create clone of an object in JavaScript

Question

In JavaScript,

var arr = [1, 2, 3, 4, 5];
var arr2 = arr.slice();

arr2 will not change if arr values are changed. That is, arr[0] = 0;, still arr2[0] == 1; // true.

Consider this:

var obj = {name: 'John', company: 'XYZ'};
var obj2 = obj; // Creates a duplicate of obj

But obj.name = 'Dave', makes obj2.name = 'Dave' as well.

How can we do a slice() operation for objects?

This is a duplicate of many, many questions. The answer depends on whether you want a deep or a shallow copy. Use the site search. — Etheryte, Dec 18 '14 at 08:18

score 1 · Accepted Answer · answered Dec 18 '14 at 08:24

To clone objects (excluding functions and prototypes) you should use structured clone.

For node.js I have found this package, but I can't tell you if it is good.

For browsers you can use this asynchronous clone function (it depends on correct implementation of postMessage):

function clone(obj, callback) {
    var from = window.location.origin;
    var wrapper = {'__clone__': true};
    wrapper.__data__ = obj;
    var listener = function(e) {
        if(e.origin === from && e.data.__clone__) {
            callback(e.data.__data__);
            window.removeEventListener('message', listener);
        }
    };
    window.addEventListener('message', listener);
    window.postMessage(wrapper, from);
}

Structured clone supports:

primitives
new String, new Boolean, new Number
new Date
new RegExp
new Blob
new File
new FileList
new ArrayBuffer
TypedArrays
ImageData
Arrays
plain objects
Map
Set

Create clone of an object in JavaScript

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