JavaScript: Add Method to Prototype

By Xah Lee. Date: . Last updated: .

This page shows you how to add method to prototype objects.

Add Method to String

Example of adding a method to String.prototype.

[see String.prototype]

// add a removeVowels method for string prototype

String.prototype.removeVowels = function () { return this.replace(/[aeiou]/g, ""); };

// example call
console.log("how are you".removeVowels()); // "hw r y"

Add Method to Array

Example of adding a method to Array.prototype.

[see Array.prototype]

// add a method to array prototype

// remove first and last item of a array, return the removed items

Array.prototype.shiftAndPop = function (){ return [this.shift(), this.pop()]; };

// test
let aa = [0,1,2,3,4];
console.log(aa.shiftAndPop()); // [0,4]
console.log(aa); // [1,2,3]

Add Method to Number

Example of adding a method to Number.prototype.

[see Number.prototype]

// add a method to the number prototype
Number.prototype.plusN = function (n) { return (this + n); };

// test
console.log( 3["plusN"](4) ); // 7

Do Not Add to Prototype Object

Note: Adding a method to prototype is not a recommended practice. Because, adding to global object changes the language unexpectedly and create conflicts if other people also do it.

[see Prototype and Inheritance]

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