Hello everyone, afternoon to you all and welcome to a new tutorial section on JavaScript. In our tutorial post we talked about JavaScript dialog boxes and I believe by now you can easily create the various dialog boxes without much stress.
In this tutorial post we are going to be discussing about JavaScript Void Keyword.
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.
In this tutorial post we are going to be discussing about JavaScript Void Keyword.
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.
Syntax
The syntax of void can be either of the following two:
<head>
<script type = "text/Javascript">
<!--
void func()
javascript:void func()
or:
void(func())
javascript:void(func())
//-->
</script>
</head>
<script type = "text/Javascript">
<!--
void func()
javascript:void func()
or:
void(func())
javascript:void(func())
//-->
</script>
</head>
You can also read our tutorial post on: JavaScript Syntax
Example 1
The most common use of this operator is in a client-side Javascript: URL, where it allows you to evaluate an expression for it's 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:
Here the expression alert('Warning!!!') is evaluated but it is not loaded back into the current document:
<html>
<head>
<script type = "text/Javascript">
<!--
//-->
</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>
<head>
<script type = "text/Javascript">
<!--
//-->
</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>
Output
Below is the output of the above example
You can also read our tutorial post on: JavaScript - while Loop
Example 2
Take a look at the following example. The following link does nothing because the expression "0" has no effect in JavaScript. Here the expression "0" is evaluated, but it is not loaded back into the current document.
<html>
<head>
<script type = "text/Javascript">
<!--
//-->
</script>
</head>
<body>
<p>Click the following, this won't react at all...</p>
<a href = "javascript:void(0)">Click Me</a>
</body>
</html>
<head>
<script type = "text/Javascript">
<!--
//-->
</script>
</head>
<body>
<p>Click the following, this won't react at all...</p>
<a href = "javascript:void(0)">Click Me</a>
</body>
</html>
Output
Below is the output of the above example
You can also read our tutorial post on: JavaScript - Loop Control
Example 3
Another use of void is to purposely generate the undefined value as follows:
<html>
<head>
<script type = "text/javascript">
<!--
function getValue() {
var a, b, c;
a = void ( b = 5, c = 7 );
document.write( ' a = ' + a + ' b = ' + b + ' c = ' + c );
}
//-->
</script>
</head>
<body>
<p>Click the following to see the result.</p>
<form>
<input type = "button" value = "ClickMe" onclick = "getValue();" />
</form>
</body>
</html>
<head>
<script type = "text/javascript">
<!--
function getValue() {
var a, b, c;
a = void ( b = 5, c = 7 );
document.write( ' a = ' + a + ' b = ' + b + ' c = ' + c );
}
//-->
</script>
</head>
<body>
<p>Click the following to see the result.</p>
<form>
<input type = "button" value = "ClickMe" onclick = "getValue();" />
</form>
</body>
</html>
Output
Below is the output of the above example
Click the following to see the result.
Alright guys, we have come to the end of this tutorial post on JavaScript void Keyword. In our next tutorial post we will be discussing about JavaScript Page Printing.
Like i always tell you guys, always feel free to ask your questions via the comment box, they will be attended to as soon as possible.
Follow us on our various social media platforms in other to stay updated with our latest tutorials. Thanks for reading and bye for now.
Like i always tell you guys, always feel free to ask your questions via the comment box, they will be attended to as soon as possible.
Follow us on our various social media platforms in other to stay updated with our latest tutorials. Thanks for reading and bye for now.