JS Where To

JavaScripts can be put in the body and in the head sections of an HTML page.

Where to Put the JavaScript

JavaScripts 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, or at a later event, such as when a user clicks a button. When this is the case we put the script inside a function, you will learn about functions in a later chapter.

Scripts in <head>

Scripts to be executed when they are called, or when an event is triggered, are placed in functions.

Put your functions in the head section, this way they are all in one place, and they do not interfere with page content.

Example

<html>
<head>
<script type="text/javascript">
function message()
{
alert("This alert box was called with the onload event");
}
</script>
</head>

<body onload="message()">
</body>
</html>

Try it yourself »

Scripts in <body>

If you don't want your script to be placed inside a function, or if your script should write page content, it should be placed in the body section.

Example

<html>
<head>
</head>

<body>
<script type="text/javascript">
document.write("This message is written by JavaScript");
</script>
</body>

</html>

Try it yourself »

Scripts in <head> and <body>

You can place an unlimited number of scripts in your document, so you can have scripts in both the body and the head section.

Example

<html>
<head>
<script type="text/javascript">
function message()
{
alert("This alert box was called with the onload event");
}
</script>
</head>

<body onload="message()">
<script type="text/javascript">
document.write("This message is written by JavaScript");
</script>
</body>

</html>

Try it yourself »

 

Using an External JavaScript

If you want to run the same JavaScript on several pages, without having to write the same script on every page, you can write a JavaScript in an external file.

Save the external JavaScript file with a .js file extension.

Note: The external script cannot contain the <script></script> tags!

To use the external script, point to the .js file in the "src" attribute of the <script> tag:

Example

<html>
<head>
<script type="text/javascript" src="/xxx.js"></script>
</head>
<body>
</body>
</html>