JS: Add Method to Prototype

Add Method to String Prototype

Example of adding a method to 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 Prototype

Example of adding a method to Array.prototype

// add a method to array prototype

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

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

// s------------------------------
// test

const xx = [0, 1, 2, 3, 4];
console.log(JSON.stringify(xx.shiftAndPop()) === "[0,4]");
console.log(JSON.stringify(xx) === "[1,2,3]");

Add Method to Number Prototype

Example of adding a method to Number.prototype

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

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

🟢 TIP: Do Not Add to Object Prototype

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〕