# JavaScript Where To

« Previous
Next Chapter »

JavaScript can be placed in the <body> and the <head> sections of an HTML page.

## The <script> Tag

In HTML, JavaScript code must be inserted between <script> and </script> tags.

## Example

<script>
document.getElementById("demo").innerHTML = "My First JavaScript";
</script>

| Older examples may use a type attribute: <script type="text/javascript">. The type attribute is not required. JavaScript is the default scripting language in HTML.

## JavaScript Functions and Events

A JavaScript function is a block of JavaScript code, that can be executed when "asked" for.

For example, a function can be executed when an event occurs, like when the user clicks a button.

You will learn much more about functions and events in later chapters.

## JavaScript in <head> or <body>

You can place any number of scripts in an HTML document.

Scripts can be placed in the <body>, or in the <head> section of an HTML page, or in both.

| Keeping all code in one place, is always a good habit.

## JavaScript in <head>

In this example, a JavaScript function is placed in the <head> section of an HTML page.

The function is invoked (called) when a button is clicked:

## Example

<!DOCTYPE html>
<html>

<head>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = "Paragraph changed.";
}
</script>
</head>

<body>

<h1>My Web Page</h1>

<p id="demo">A Paragraph</p>

<button type="button" onclick="myFunction()">Try it</button>

</body>
</html>

Try it Yourself »

## JavaScript in <body>

In this example, a JavaScript function is placed in the <body> section of an HTML page.

The function is invoked (called) when a button is clicked:

## Example

<!DOCTYPE html>
<html>
<body>
<h1>My Web Page</h1>
<p id="demo">A Paragraph</p>
<button type="button" onclick="myFunction()">Try it</button>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = "Paragraph changed.";
}
</script>
</body>
</html>
Try it Yourself »

| It is a good idea to place scripts at the bottom of the <body> element. This can improve page load, because HTML display is not blocked by scripts loading.

## External JavaScript

Scripts can also be placed in external files.

External scripts are practical when the same code is used in many different web pages.

JavaScript files have the file extension .js.

To use an external script, put the name of the script file in the src (source) attribute of the <script> tag:

## Example

<!DOCTYPE html>
<html>
<body>
<script src="myScript.js"></script>
</body>
</html>
Try it Yourself »

You can place an external script reference in <head> or <body> as you like.

The script will behave as if it was located exactly where the <script> tag is located.

| External scripts cannot contain <script> tags.

## External JavaScript Advantages

Placing JavaScripts in external files has some advantages:

- It separates HTML and code.
- It makes HTML and JavaScript easier to read and maintain
- Cached JavaScript files can speed up page loads.

« Previous
Next Chapter »

### WEB HOSTING

UK Reseller Hosting

### WEB BUILDING

FREE Website BUILDER Free HTML5 Templates

### W3SCHOOLS EXAMS

HTML, CSS, JavaScript, PHP, jQuery, XML, and ASP Certifications

### SHARE THIS PAGE

### Color Picker

### HTML/CSS

HTML Tutorial HTML5 Tutorial CSS Tutorial CSS3 Tutorial Bootstrap Tutorial

### JavaScript

JavaScript Tutorial jQuery Tutorial jQuery Mobile Tutorial AngularJS Tutorial AJAX Tutorial JSON Tutorial

### Graphics

Canvas Tutorial SVG Tutorial Google Maps Tutorial

### Server Side

SQL Tutorial PHP Tutorial ASP Tutorial ASP.NET Tutorial VBScript Tutorial AppML Tutorial

### Web

Web Building Web Statistics Web Certification

### XML

XML Tutorial DTD Tutorial Schema Tutorial XML DOM Tutorial XPath Tutorial XSLT Tutorial XQuery Tutorial XSL-FO Tutorial RSS Tutorial WSDL Tutorial

### HTML/CSS

HTML Tag Reference HTML Event Reference HTML Color Reference CSS 1,2,3 Reference Bootstrap Reference

### JavaScript

JavaScript Reference HTML DOM Reference jQuery Reference jQuery Mobile Reference Google Maps Reference

### Server Side

PHP Reference SQL Reference ASP Reference VBScript Reference Razor Reference ASP.NET Reference

### XML

XML DOM Reference XSLT Reference XSL-FO Reference XPath Reference XQuery Reference Schema Reference RSS Reference SVG Reference

### HTML Charsets

HTML Character Sets HTML ASCII HTML ANSI HTML Windows-1252 HTML ISO-8859-1 HTML Symbols HTML UTF-8

### HTML/CSS

HTML Examples CSS Examples

### Browser Scripting

JavaScript Examples HTML DOM Examples jQuery Examples jQuery Mobile Examples AngularJS Examples AJAX Examples

### Server Scripting

PHP Examples ASP Examples VBScript Examples Razor Examples .NET Examples

### XML Languages

XML Examples DTD Examples XML DOM Examples XSL Examples XSLT Examples XPath Examples XQuery Examples Schema Examples RSS Examples SVG Examples