Is it required to have a return a value from a JavaScript function?

A JavaScript function can have an optional return statement i.e. it’s optional to return a value. This statement should be the last statement in a function.

For example, you can pass two numbers in a function and then you can expect the function to return their multiplication to your calling program.

Example

Try the following example. It defines a function that takes two parameters and concatenates them before returning the resultant in the calling program.

Live Demo

<html>
<script type = "text/javascript">
function concatenate(first, last){
var full;

full = first + last;
return full;
}
function secondFunction(){
var result;
result = concatenate('John', 'Doe');
document.write (result );
}
</script>

<body>
<p>Click the following button to call the function</p>
<form>
<input type = "button" onclick = "secondFunction()" value = "Call Function">
</form>
<p>Use different parameters inside the function and then try...</p>
</body>

</html>