Following is a list of just some of the features which include in a web page.
Animations -Some animation can be achieved with CSS transitions, but for true interactivity, you need to control graphics directly using Javascript.
Geolocation - To provide location-aware services to your users, you must access the data using Javascript.
Canvas - The only way to draw on the HTML5 canvas is with Javascript commands.
Audio and Video - You can add these with simple HTML5 tags, but to control playback directly, you will need Javascript.
Form processing - If you wish to make your forms easier to use by having in-browser validation, user prompting, and error checking, then you have to do much of this with JavaScript, although HTML5 is making some great inroads in this direction.
Ajax - Any behind-the-scenes communication with a web server you need to make has to be done via JavaScript calls.
Dynamic Elements - Some elements can be changed via CSS and mouse-overs, but for anything more, such as resizing, moving, or dragging and dropping, you have to use JavaScript.
In-browser Gaming - Games that run in the browser without plug-ins such as Flash are written in JavaScript.
Floating Elements - Pop-ups and other floating elements that follow the page as you scroll are all implemented with JavaScript.
Hover Effects - Thumbnail or advanced tooltips that hover over HTML elements are created and controlled with JavaScript.
