The void is an important keyword in JavaScript, which can be used as a unary operator that appears before its single operand, which may be of any type. This operator specifies an expression to be evaluated without returning a value.
The syntax of the void can be either of the following two −
<head> <script> <!-- void func() javascript:void func() or: void(func()) javascript:void(func()) //--> </script> </head>
The most common use of this operator is in a client-side javascript: URL, where it allows you to evaluate an expression for its side-effects without the browser displaying the value of the evaluated expression.
Here the expression alert ('Warning!!!') is evaluated but it is not loaded back into the current document.
Example
<html>
<head>
<script>
<!--
//-->
</script>
</head>
<body>
<p>Click the following, This won't react at all...</p>
<a href="javascript:void(alert('Warning!!!'))">Click me!</a>
</body>
</html>