HTML JavaScript

JavaScript makes HTML pages more dynamic and interactive.

Example

My First JavaScript

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The HTML <script> Tag

The <script> tag is used to define a client-side script (JavaScript).

The <script> element either contains scripting statements, or it points to an external script file through the srcattribute.

Common uses for JavaScript are image manipulation, form validation, and dynamic changes of content.

To select an HTML element, JavaScript very often use the document.getElementById(id) method.

This JavaScript example writes "Hello JavaScript!" into an HTML element with id="demo":

Example

<script>
document.getElementById("demo").innerHTML = "Hello JavaScript!";</script>

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A Taste of JavaScript

Here are some examples of what JavaScript can do:

JavaScript can change HTML content

document.getElementById("demo").innerHTML = "Hello JavaScript!";

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JavaScript can change HTML styles

document.getElementById("demo").style.fontSize = "25px";
document.getElementById("demo").style.color = "red";
document.getElementById("demo").style.backgroundColor = "yellow";

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JavaScript can change HTML attributes

document.getElementById("image").src = "picture.gif";

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The HTML <noscript> Tag

The <noscript> tag is used to provide an alternate content for users that have disabled scripts in their browser or have a browser that doesn't support client-side scripts:

Example

<script>
document.getElementById("demo").innerHTML = "Hello JavaScript!";</script>

<noscript>Sorry, your browser does not support JavaScript!</noscript>

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HTML Script Tags

Tag	Description
<script>	Defines a client-side script
<noscript>	Defines an alternate content for users that do not support client-side scripts