angularjs之$timeout指令详解
angular.js的$timeout指令对window.setTimeout做了一个封装,它的返回值是一个promise对象.当定义的时间到了以后,这个promise对象就会被resolve,回调函数就会被执行.
如果需要取消一个timeout,调用$timeout.cancel(promise)方法.
用法:
$timeout(fn, [delay], [invokeApply]);
fn: 回调函数(必填)
delay: number类型.延迟的时间(非必填),如果不填,表示等线程空下来以后就执行.比如当页面被渲染完成后.
invokeApply: 布尔值.是否需要进行脏值检测(非必填),不填默认为false,如果设置为true,则fn回调会被包在$scope.$apply()中执行
返回值: 返回一个promise对象.当定义的时间到了以后,这个promise对象就会被resolve.resolve的值就是fn回调函数的返回值
方法:
$timeout.cancel([promise])
promise: 一个由$timeout()所创建的promise对象.(非必填).调用cancel()以后,这个promise对象就会被reject.
返回值: 如果$timeout()的回调还没有被执行,那就取消成功.返回true
下面来简单的测试一下:
var timeoutApp = angular.module('timeoutApp',[]);
timeoutApp.run(function($timeout){
var a = $timeout(function(){
console.log('执行$timeout回调');
return 'angular'
},1000);
a.then(function(data){
console.log(data)
},function(data){
console.log(data)
});
//$timeout.cancel(a);
})运行以后看到控制台打印:
执行$timeout回调
angular
如果我打开注释,执行.cancel()方法,那么$timeout的回调就不会被执行,它返回的promise被reject,控制台打印:
canceled
下面做个很实用的小demo: 延迟下拉菜单: 鼠标放到button上的时候,延迟500毫秒显示下拉菜单,当鼠标离开button的时候,延迟500毫秒隐藏下拉菜单,如果鼠标是进入了下拉菜单部分,那么就不隐藏下拉菜单.如果鼠标离开了下拉菜单,延迟500毫秒隐藏下拉菜单,如果鼠标是进入了button,那么还是不隐藏下拉菜单
html:
<!DOCTYPE html>
<html ng-app="timeoutApp">
<head>
<title>$timeout服务</title>
<meta charset="utf-8">
<link rel="stylesheet" href="../bootstrap.css" rel="external nofollow" />
<script src="../angular.js"></script>
<script src="script.js"></script>
<style type="text/css">
* {
font-family:'MICROSOFT YAHEI'
}
</style>
</head>
<body >
<div ng-controller="myCtrl">
<div class="dropdown" dropdown >
<button class="btn btn-default dropdown-toggle" type="button" ng-mouseenter = "showMenu()" ng-mouseleave = "hideMenu()">
Dropdown
<span class="caret"></span>
</button>
<ul class="dropdown-menu" ng-show="ifShowMenu" ng-mouseenter = "showMenu()" ng-mouseleave = "hideMenu()">
<li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >Action</a></li>
<li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >Another action</a></li>
<li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >Something else here</a></li>
<li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >Separated link</a></li>
</ul>
</div>
</div>
</body>
</html>js:
var timeoutApp = angular.module('timeoutApp',[]);
timeoutApp.controller('myCtrl',function($scope){
$scope.ifShowMenu = false;
});
timeoutApp.directive('dropdown',function($timeout){
return {
restrict:"EA",
link:function(scope,iele,iattr){
scope.showMenu = function(){
$timeout.cancel(scope.t2);
scope.t1 = $timeout(function(){
scope.ifShowMenu = true
},500)
};
scope.hideMenu = function(){
$timeout.cancel(scope.t1);
scope.t2 = $timeout(function(){
scope.ifShowMenu = false
},500)
};
}
}
})代码应该很好理解: 就是进入button和进入ul下拉菜单的时候,都定义一个timeout回调(过500毫秒以后显示下拉菜单),同时取消隐藏下拉菜单的回调.而离开button和ul的时候相反.
代码地址: https://github.com/OOP-Code-Bunny/angular/tree/master/%24timeout