Passing Functions as Arguments part 1

var doSomething = function(paramOne, paramTwo, fn) {
  paramOne = paramOne * 8;
  // return the result of calling this function
  return fn(paramOne, paramTwo);
};

function sum(paramOne, paramTwo) {
  // add the passed in arguments and return the value
  return paramOne + paramTwo;
}

// set one
// argument 3 is a reference to the predefined function
// with the name "sum"
var foo = doSomething(2, 2, sum);
// if that function didnt already exist we could define
// and inject it directly into doSomething when we call it
// So the beneath would be exactly equivalent because the 
// function you define on the spot is the same as the 
// predefined sum function
var bar = doSomething(2, 2, function(paramOne, paramTwo) {
  return paramOne + paramTwo;
});
// and thats all we are doing in set two

// if we consider primitive variables the concept is the same
// we can have variable x containing value 5
var x = 5;
// then alert it
alert(x);
// here variable x and its value are predined but if it wasnt
// we could simply insert it into the alert function as we call it
alert (5);
// no need for a predefined variable just like no need for a
// predefined function in set two 

// set two
var bar = doSomething(3, 4, function(paramOne, paramTwo) {
  return paramOne * paramTwo;
});

Test code at jsbin