JavaScript makes HTML pages more dynamic and interactive.
See the Pen
HTML JavaScript by Iampsp.com (@iampsp)
on CodePen.
The HTML <script> Tag
The HTML <script> tag is used to define a client-side script (JavaScript).
The <script> element either contains script statements, or it points to an external script file through the src attribute.
Common uses for JavaScript are image manipulation, form validation, and dynamic changes of content.
To select an HTML element, JavaScript most often uses the document.getElementById() method.
This JavaScript example writes “Hello JavaScript!” into an HTML element with id=”demo”:
<script>
document.getElementById("demo").innerHTML = "Hello JavaScript!";
</script>
A Taste of JavaScript
Here are some examples of what JavaScript can do:
JavaScript can change content:
document.getElementById("demo").innerHTML = "Hello JavaScript!";
JavaScript can change styles:
document.getElementById("demo").style.fontSize = "25px";
document.getElementById("demo").style.color = "red";
document.getElementById("demo").style.backgroundColor = "yellow";
JavaScript can change attributes:
document.getElementById("image").src = "picture.gif";
The HTML <noscript> Tag
The HTML <noscript> tag defines an alternate content to be displayed to users that have disabled scripts in their browser or have a browser that doesn’t support scripts:
<script>
document.getElementById("demo").innerHTML = "Hello JavaScript!";
</script>
<noscript>Sorry, your browser does not support JavaScript!</noscript>