extend Object/String/Number/Array using prototype

extend classes using prototype.js

// all objects inherit methods and properties from Object.prototype, although they may be overridden

Object.prototype.toSource()
// "({})"

str = 'hello';
arr = new Array(20);
num = 99;

Object.prototype.boom = function() {
  return 'pow';
};

Number.prototype.boom = function() {
  return NaN;
}

console.log(str.boom());  // pow
console.log(arr.boom());  // pow
console.log(num.boom());  // NaN

String.prototype.myFooProp = 'dingle';

console.log( arr.myFooProp );  // undefined
console.log( str.myFooProp );  // dingle

Object.prototype.whatAmI = function() {
  if (this.constructor == Array) {
    return "I'm an array!!!";
  }
  
  if (this.constructor === String) {
    return "I'm a string!!!";
  }
};

console.log( arr.whatAmI() );  // I'm an array!!!
console.log( str.whatAmI() );  // I'm a string!!!

global default.js

    Object.prototype.foo = 10; 
    console.log(foo); // 10