Uses of JavaScript

• Adds interactivity to web pages
• Run codes in response to certain events
• JavaScript has a powerful Application Programming Interface (APIs), hence access to numerous complex features

What is even more exciting however is the functionality built on top of the client-side JavaScript language. So-called Application Programming Interfaces (APIs) provide you with extra superpowers to use in your JavaScript code.

APIs are ready-made sets of code building blocks that allow a developer to implement programs that would otherwise be hard or impossible to implement. They do the same thing for programming that ready-made furniture kits do for home building 

There are two types of APIs available:

•  Browser APIs: Built and shipped with Browsers
• Third party APIs: Not built into the browser by default, and you generally have to grab their code and information from somewhere on the Web. For example: Google maps API, Twitter API