Nested Functions

Since a function returns a value, it can also return a function as value. So we can define a function inside another function and return it.

In the example below, we define a function called inner(), which returns a random number, inside a function called outer()

js nested functions 
				
				function outer(){
					function inner(){
						return Math.random(); 
					}
					return inner;
				}

The same can be written in function literal notation as 

				
				var outer = function() {
					var inner = function(){
						return Math.random(); 
					}
					return inner;
				}

The inner() function cannot be accessed directly outside of the outer() function. But the outer() function returns a value which can be assigned to a variable, which can then be called as a normal function as shown below 

				
				var inside = outer();
				inside();

The inner() function can also be called by using another set of parentheses while calling outer() as 

				outer()();

Below, we illustrate the same by passing numerical arguments to both outer() and inner() functions and then returning their sum

				
				function outer(x){
					function inner(y){
						return x+y; 
					}
					return inner;
				}

inside(1) returns the value 2 

				
				var inside = outer(1);
				inside(1);

which can also be achieved by the following call 

				
					outer(1)(1);