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 src attribute.
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:
<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML = "Hello JavaScript!";
</script>
</body>
</html>
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:
<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML = "Hello JavaScript!";
</script>
<noscript>Sorry, your browser does not support JavaScript!</noscript>
<p>A browser without support for JavaScript will show the text written inside the noscript element.</p>
</body>
</html>
Also Example:
<!DOCTYPE html>
<html>
<body>
<script>
function light(sw) {
var pic;
if (sw == 0) {
pic = "pic_bulboff.gif"
} else {
pic = "pic_bulbon.gif"
}
document.getElementById('myImage').src = pic;
}
</script>
<img id="myImage" src="pic_bulboff.gif" width="100" height="180">
<p>
<button type="button" onclick="light(1)">Light On</button>
<button type="button" onclick="light(0)">Light Off</button>
</p>
</body>
</html>
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