Functions in javaScript

We've already seen and used javaScript functions is this course. Let's take the opportunity at this stage to look into them in a little more depth.

• Functions are named collections of statements
• javaScript has built-in functions, and you can write your own

• For example parseInt() parses a string and returns an integer

       //this is not a number it's a string , as it's in "" marks 
       var firstNumber = "12";       
       //number1 will hold the numeric value 12
       number1 = parseInt(firstNumber);
  

• A function contains code that will be executed by an event or by a call to the function

How To Define A Function

 function functionName(var1, var2, ...)
 { //some code;
 }

Function's can also return values

function numberProduct(num1, num2) {
   var result = num1 * num2;
   return result;

}

var product = numberProduct(2,4);
console.log(product); // will output 8 to the console

• The parameters num1 and num2 are variables or values passed into the function. You can have as many parameters as you like.
• A function with no parameters must still include ( ) after the function name
• The word function must be written in lowercase letters in your code
• You must call a function with the exact same capitals as in the function definition