JavaScript in HTML: The script Element

JavaScript makes pages interactive. You add it to HTML with the script element.

Inline script

index.html

HTML

<p id="greeting">Hello.</p>
<script>
  document.getElementById("greeting").textContent = "Hello from JavaScript.";
</script>

The script finds the element with the id greeting and changes its text.

External script

For anything bigger, put the code in a file and load it with src.

index.html

HTML

<script src="app.js"></script>

An external script file is cached by the browser and can be used on many pages. The script tag still needs a closing tag, even with src.

noscript

noscript shows content when JavaScript is turned off or fails to load.

index.html

HTML

<noscript>This feature needs JavaScript. Please turn it on.</noscript>

info

HTML first

A good page works without JavaScript as far as possible. Content, links and forms should be real HTML. Use JavaScript to improve them, not to create them from nothing.

warning

Forgetting the closing tag

<script src="app.js" /> is not valid HTML. Write <script src="app.js"></script>.