Function Declaration

Also called a function statement.
This always starts with the keyword "function".
This creates a variable called IsEven in the current scope that holds the function object.
You do not have to put a semicolon at the end.

function IsEven(num) { 
   return num % 2 === 0; 
} 
console.log(IsEven(2)); 

Named Function Decelaration - without Arguments

function doSomething() { 
   alert('my message'); 
} 

doSomething(); 

Named Function Decelaration - with Arguments

This function takes 2 parameters
Often called the standard function declaration

function add(x, y) 
{ 
   var z = x + y; 
   return z; 
} 

var sum = add(1,2)