JS: 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 JS: 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 JS: 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 JS: 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 JS: Prototype and Inheritance]

Object and Inheritance Topic

  1. JS: Object Overview
  2. JS: Object Type
  3. JS: Determine Type of Object
  4. JS: Object Literal Expression
  5. JS: Prototype and Inheritance
  6. JS: Create Object
  7. JS: Create Object with Parent X
  8. JS: Get/Set Prototype
  9. JS: Prevent Adding Property
  10. JS: Clone, Deep Copy Object/Array
  11. JS: Test Equality of Objects
  12. JS: Object Object
  13. JS: Object.prototype

JS Constructor Topic

  1. JS: “this” Binding
  2. JS: What's Constructor?
  3. JS: Property Key "prototype"
  4. JS: Operator “new”
  5. JS: “instanceof” Operator
  6. JS: Property Key “constructor”
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