Angular4 - Introduction

      What is Angular?

      AngularJS is a structural framework for dynamic web apps. It lets you use HTML as your template language and lets you extend HTML's syntax to express your application's components clearly and succinctly. AngularJS's data binding and dependency injection eliminate much of the code you would otherwise have to write. And it handles all of the DOM and AJAX code you once wrote by hand and puts it in a well-defined structure.

• History: AJAX -> jQuery / Prototype -> MVC Frameworks (Knockout / Backbone) -> AngularJS
• AngularJS is a very powerful open source and absolutely free JavaScript library distributed as   Angular.js file. 
• It's majorly used for developing Single Page Applications (SPA). 
• It's based on Model View Controller design pattern.
• It's an extension of HTML DOM and has additional attributes which reduces code and makes it easy to program dynamic and responsive applications.
• Its features include everything we need to build a CRUD app: data-binding, basic templating, directives, form validation, routing, deep-linking, reusable components, dependency injection.
• Angular is built around the belief that declarative code is better than imperative when it comes to building UIs and wiring software components together, while imperative code is excellent for expressing business logic.
• In AngularJS, views are pure html pages, and controllers written in JavaScript do the business processing.
• AngularJS applications can run on all major browsers and smart phones, including Android and IOS based phones/tablets.