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JavaScript How To

The HTML <script> tag is used to insert a JavaScript into an HTML page.

Examples

Write text with Javascript
The example demonstrates how to use JavaSript to write text on a web page.

Write HTML with Javascript
The example demonstrates how to use JavaScript to write HTML tags on a web page.

How to Put a JavaScript Into an HTML Page

<html>
<body>
<script type="text/javascript">
document.write("Hello World!");
</script>
</body>
</html>

The code above will produce this output on an HTML page:

Hello World!

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 word document.write 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>

Try it yourself.

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.

HTML Comments 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 can be used to "hide" the JavaScript. Just add an HTML comment tag  (end of comment) after the last JavaScript statement.

<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.