angularjs 引入 controller as 的疑问？

之前了解过1.2x版本引入了controller as 的语法。

var app = angular.module('app', []);

app.controller('demoController', [function(){
    this.title = 'angular';
}])


html: 

<div ng-app="app" ng-controller="demoController as demo">
    hello: {{demo.title}}
</div>

引入这个语法糖有什么作用呢？以及不同的适用场景？

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http://stackoverflow.com/questions/11605917/this-vs-scope-in-angularjs-controllers

http://www.cnblogs.com/whitewolf/p/3493362.html