JavaScript How To...
The HTML <script> tag is used to insert a JavaScript into an HTML 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:
Example Explained
To insert a JavaScript into an HTML page, we use the <script> tag (also 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 type="text/javascript"> 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.
Ending Statements With a Semicolon?
With traditional programming languages, like C++ and Java, each code statement has to end with a semicolon.
Many programmers continue this habit when writing JavaScript, but in general, semicolons are optional! However, semicolons are required if you want to put more than one statement on a single line.
How to Handle Older Browsers
Browsers that do not support JavaScript will display the script as page content. To prevent them from doing this, we may use the HTML comment tag:
<script type="text/javascript">
<!--
document.write("Hello World!")
//-->
</script> |
The two forward slashes at the end of comment line (//) are a JavaScript comment symbol. This prevents the JavaScript compiler from compiling the line. |
