JavaScript How To
The HTML <script> tag is used to insert a JavaScript into an HTML page.
Put a JavaScript into an HTML page
The example below shows how to use JavaSript to write text on a web page:
Example
<html>
<body>
<script type="text/javascript">
document.write("Hello World!");
</script>
</body>
</html>
|
Try it yourself »
|
The example below shows how to add HTML tags to the JavaScript:
Example
<html>
<body>
<script type="text/javascript">
document.write("<h1>Hello World!</h1>");
</script>
</body>
</html>
|
Try it yourself »
|
Example Explained
To insert a JavaScript into an HTML page, we use the <script> tag. Inside the <script> tag we
use the type attribute to define the scripting language.
So, the <script type="text/javascript"> and </script> tells where the JavaScript starts and ends:
<html>
<body>
<script type="text/javascript">
...
</script>
</body>
</html> |
The document.write command is a standard JavaScript command for writing output to a page.
By entering the document.write command between the <script> and </script> tags, the browser will recognize it as a JavaScript command and
execute the code line. In this case the browser will write Hello World! to the page:
<html>
<body>
<script type="text/javascript">
document.write("Hello World!");
</script>
</body>
</html> |
Note: If we had not entered the <script> tag, the browser would have
treated the document.write("Hello World!") command as pure text, and just write the entire line on the page.
Try it yourself
How to Handle Simple Browsers
Browsers that do not support JavaScript, will display JavaScript as page content.
To prevent them from doing this, and as a part of the JavaScript standard, the HTML comment tag should be used to "hide" the JavaScript.
Just add an HTML comment tag <!-- before the first JavaScript statement, and a --> (end of comment) after the last JavaScript statement, like this:
<html>
<body>
<script type="text/javascript">
<!--
document.write("Hello World!");
//-->
</script>
</body>
</html> |
The two forward slashes at the end of comment line (//) is the JavaScript comment symbol. This prevents JavaScript from executing the --> tag.
 |
W3Schools' Online Certification Program
The perfect solution for professionals who need to balance work, family, and career building.
More than 4000 certificates already issued!
|
The HTML Certificate documents your knowledge of HTML, XHTML, and CSS.
The JavaScript Certificate documents your knowledge of JavaScript and HTML DOM.
The XML Certificate documents your knowledge of XML, XML DOM and XSLT.
The ASP Certificate documents your knowledge of ASP, SQL, and ADO.
The PHP Certificate documents your knowledge of PHP and SQL (MySQL).
| 
