Function in JavaScript

A function allows us to write code once and we can use it as many times as our wish just by calling the function. A function eliminates the need of writing the same code again and again.

Syntax:

function functionName(parameter1, parameter2,..parameter_n)
    {
    //function statements
    }

Example:

<script type="text/javascript">
    function addNumbers(firstNumber, secondNumber) {
        var result = firstNumber + secondNumber;
        return result;
    }

   var sum = addNumbers(10, 20);
   alert(sum);
   </script>

Output:

30