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