1、问题背景
AngularJS中的$watch方法来监听数据变化
2、实现源码
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>AngularJS之$watch方法（监控动作）</title>
<script src="http://apps.bdimg.com/libs/angular.js/1.4.6/angular.min.js"></script>
<style>
body{
font-size: 12px;
font-family: "微软雅黑";
background-color: #F8EFC0;
backface-visibility: visible;
}
div{
margin: 10px 10px 10px 10px;
}
</style>
<script>
var app = angular.module("watchApp",[]);
app.controller("watchCon",['$scope',function($scope){
$scope.count = 0;
$scope.username = "";
$scope.$watch('username',function(){
$scope.count++;
});
}]);
</script>
</head>
<body ng-app="watchApp">
<div ng-controller="watchCon">
<div>
<input type="text" id="username" ng-model="username" maxlength="12" autocomplete="on"/>
</div>
<div>
{{count}}
</div>
</div>
</body>
</html>
3、实现结果
（1）初始化
（2）改变输入框值
