JavaScript Functions

JavaScript functions are used to perform operations. We can call JavaScript function many times to reuse the code.

There are mainly two advantages of JavaScript functions.

Code reusability: We can call a function several times so it save coding.
Less coding: It makes our program compact. We don’t need to write many lines of code each time to perform a common task.

JavaScript Function Syntax

The syntax of declaring function is given below.

function functionName([arg1, arg2, ...argN]){
 //code to be executed
}

JavaScript Functions can have 0 or more arguments.

Let’s see the simple example of function in JavaScript that does not has arguments.

<script>
function msg(){
alert("hello! this is message");
}
</script>
<input type="button" onclick="msg()" value="call function"/>

We can call function by passing arguments. Let’s see the example of function that has one argument.

<script>
function getcube(number){
alert(number*number*number);
}
</script>
<form>
<input type="button" value="click" onclick="getcube(4)"/>
</form>

We can call function that returns a value and use it in our program. Let’s see the example of function that returns value.

<script>
function getInfo(){
return "hello javatpoint! How r u?";
}
</script>
<script>
document.write(getInfo());
</script>