How Do I Copy A Map Into A Duplicate Map?

How do I clone/copy a map in JavaScript? I know how to clone an array but how do I clone/copy a map? var myArray = new Array(1, 2, 3); var copy = myArray.slice(); // now I can c

Solution 1:

With the introduction of Maps in JavaScript it's quite simple considering the constructor accepts an iterable:

var newMap = newMap(existingMap)

Documentation here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map

Solution 2:

A simple way (to do a shallow copy) is to copy each property of the source map to the target map:

var newMap = {};
for (var i in myMap)
   newMap[i] = myMap[i];

NOTE: newMap[i] could very well be a reference to the same object as myMap[i]

Solution 3:

Very simple to clone a map since what you're talking about is just an object. There is a Map in ES6 that you should look up, but to copy an object, just use Object.assign()

let map = {"a": 1, "b": 2}
let copy = Object.assign({}, map);

You can also use cloneDeep() from Lodash

let copy = cloneDeep(map);

Solution 4:

JQuery has a method to extend an object (merging two objects), but this method can also be used to clone an object by providing an empty object.

// Shallow copyvar newObject = jQuery.extend({}, oldObject);

// Deep copyvar newObject = jQuery.extend(true, {}, oldObject);

More information can be found in the jQuery documentation.

Solution 5:

There is nothing built in.

Either use a well tested recursive property copier or if performance isn't an issue, serialise to JSON and parse again to a new object.