Consider the following code snippet

function hypotenuse(a, b) 
{
  function square(x) 
  { 
    return x*x; 
  }
  return Math.sqrt(square(a) + square(b));
}

What does the above code result?

The above code snippet contains nested function in which the function hypotenuse(a,b) has another function inside its scope, function square(x). The interesting thing about nested functions is their variable scoping rules. They can acceess the parameters and variables of the function (or functions) they are nested within.