Scope

Data binding in AngularJS is achieved using the scope object. We can attach properties to it and explicitly declare in the template that we want to bind to these properties (one- or two-way). Although the idea of the scope seems clear, it has two more responsibilities, including event dispatching and the change detection-related behavior.

Angular beginners have a hard time understanding what scope really is and how it should be used. AngularJS 1.2 introduced something called controller as syntax. It allows us to add properties to the current context inside the given controller (this), instead of explicitly injecting the scope object and later adding properties to it. This simplified syntax can be demonstrated through the following snippet:

<div ng-controller="MainCtrl as main"> 
  <button ng-click="main.clicked()">Click</button> 
</div>

function MainCtrl() { 
  this.name = 'Foobar'; 
} 
MainCtrl.prototype.clicked = function () { 
  alert('You clicked me!'); 
}; 

The latest Angular took this even further by removing the scope object. All the expressions are evaluated in the context of the given UI component. Removing the entire scope API introduces higher simplicity; we don't need to explicitly inject it anymore, instead, we add properties to the UI components to which we can later bind. This API feels much simpler and more natural.

We will take a more detailed look at the components and the change detection mechanism of Angular in Chapter 5, Getting Started with Angular Components and Directives.