3 ways to declare a function in javascript

javascript_function_builders.md

###Using Function constructor

    var sum = new Function('a','b', 'return a + b;');
    alert(sum(10, 20)); //alerts 30

###Using Function declaration.

    function sum(a, b) 
    {
        return a + b;
    }
    alert(sum(10, 10)); //alerts 20;

###Function Expression

    var sum = function(a, b) { return a + b; }
    alert(sum(5, 5)); // alerts 10