JavaScript Class
Where to Put the JavaScript
Scripts in a page will be executed immediately while the page loads into the
browser. This is not always what we want. Sometimes we want to execute a script
when a page loads, other times when a user triggers an event.
Body versus Head
Scripts in the body section will execute while the page
loads.
Scripts in the head section will be executed when called.
Scripts in the head section: Scripts to be executed when they are
called, or when an event is triggered, go in the head section. When you place a
script in the head section, you will ensure that the script is loaded before
anyone uses it.
<html>
<head>
<script language="JavaScript" type="text/javascript">
some statements
</script>
</head> |
Scripts in the body section: Scripts to be executed when the page
loads go in the body section. When you place a script in the body section it
generates the content of the page.
<html>
<head>
</head>
<body>
<script language="JavaScript" type="text/javascript">
some statements
</script>
</body> |
Scripts in both the body and the head section: You can place an
unlimited number of scripts in your document, so you can have scripts in both
the body and the head section.
<html>
<head>
<script language="JavaScript" type="text/javascript">
some statements
</script>
</head>
<body>
<script language="JavaScript" type="text/javascript">
some statements
</script>
</body> |
How to Run an External JavaScript
Sometimes you might want to run the same script on several pages, without
writing the script on each and every page.
To simplify this you can write a script in an external file, and save it with
a .js file extension, like this:
document.write("This script is external") |
Save the external file as xxx.js.
Note: The external script cannot contain the <script> tag
Now you can call this script, using the "src" attribute, from any of your
pages:
<html>
<head>
</head>
<body>
<script src="xxx.js"></script>
</body>
</html> |
Remember to place the script exactly where you normally would write the
script.
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