Javascript: bind, call & apply.md

1. The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called. Function.prototype.bind()

   var module = {
     x: 42,
     getX: function() {
       return this.x;
     }
   }
   
   var unboundGetX = module.getX;
   console.log(unboundGetX()); // The function gets invoked at the global scope
   // expected output: undefined
   
   var boundGetX = unboundGetX.bind(module);
   console.log(boundGetX());
   // expected output: 42
   

2. The call() method calls a function with a given this value and arguments provided individually.

   function Product(name, price) {
     this.name = name;
     this.price = price;
   }
   
   function Food(name, price) {
     Product.call(this, name, price);
     this.category = 'food';
   }
   
   console.log(new Food('cheese', 5).name);
   // expected output: "cheese"
   

3. The apply() method calls a function with a given this value, and arguments provided as an array (or an array-like object).

   var numbers = [5, 6, 2, 3, 7];
   
   var max = Math.max.apply(null, numbers);
   
   console.log(max);
   // expected output: 7
   
   var min = Math.min.apply(null, numbers);
   
   console.log(min);
   // expected output: 2
   

Note: While the syntax of this function is almost identical to that of call(), the fundamental difference is that call() accepts an argument list, while apply() accepts a single array of arguments.