What is the most efficient way to deep clone an object in JavaScript?

you could try:

function clone(obj) {

    if (obj === null || typeof (obj) !== 'object' || 'isActiveClone' in obj)

        return obj;



    if (obj instanceof Date)

        var temp = new obj.constructor(); //or new Date(obj);

    else

        var temp = obj.constructor();



    for (var key in obj) {

        if (Object.prototype.hasOwnProperty.call(obj, key)) {

            obj['isActiveClone'] = null;

            temp[key] = clone(obj[key]);

            delete obj['isActiveClone'];

        }

    }

    return temp;

}

3 years ago

Cloning an Object was always a concern in JS, but it was all about before ES6, I list different ways of copying an object in JavaScript below, imagine you have the Object below and would like to have a deep copy of that:

var obj = {a:1, b:2, c:3, d:4};

There are few ways to copy this object, without changing the origin:

ES5+, Using a simple function to do the copy for you:

    function deepCopyObj(obj) {

        if (null == obj || "object" != typeof obj) return obj;

        if (obj instanceof Date) {

            var copy = new Date();

            copy.setTime(obj.getTime());

            return copy;

        }

        if (obj instanceof Array) {

            var copy = [];

            for (var i = 0, len = obj.length; i < len; i++) {

                copy[i] = deepCopyObj(obj[i]);

            }

            return copy;

        }

        if (obj instanceof Object) {

            var copy = {};

            for (var attr in obj) {

                if (obj.hasOwnProperty(attr)) copy[attr] = deepCopyObj(obj[attr]);

            }

            return copy;

        }

        throw new Error("Unable to copy obj this object.");

    }

ES5+, using JSON.parse and JSON.stringify.

    var  deepCopyObj = JSON.parse(JSON.stringify(obj));

AngularJs:

    var  deepCopyObj = angular.copy(obj);

jQuery:

    var deepCopyObj = jQuery.extend(true, {}, obj);

UnderscoreJs & Loadash:

    var deepCopyObj = _.cloneDeep(obj); //latest version UndescoreJs makes shallow copy

3 years ago