angular.js的$timeout指令對window.setTimeout做了一個封裝,它的返回值是一個promise對象.當(dāng)定義的時間到了以后,這個promise對象就會被resolve,回調(diào)函數(shù)就會被執(zhí)行.
如果需要取消一個timeout,調(diào)用$timeout.cancel(promise)方法.
用法:
$timeout(fn, [delay], [invokeApply]);
fn: 回調(diào)函數(shù)(必填)
delay: number類型.延遲的時間(非必填),如果不填,表示等線程空下來以后就執(zhí)行.比如當(dāng)頁面被渲染完成后.
invokeApply: 布爾值.是否需要進(jìn)行臟值檢測(非必填),不填默認(rèn)為false,如果設(shè)置為true,則fn回調(diào)會被包在$scope.$apply()中執(zhí)行
返回值: 返回一個promise對象.當(dāng)定義的時間到了以后,這個promise對象就會被resolve.resolve的值就是fn回調(diào)函數(shù)的返回值
方法:
$timeout.cancel([promise])
promise: 一個由$timeout()所創(chuàng)建的promise對象.(非必填).調(diào)用cancel()以后,這個promise對象就會被reject.
返回值: 如果$timeout()的回調(diào)還沒有被執(zhí)行,那就取消成功.返回true
下面來簡單的測試一下:
var timeoutApp = angular.module('timeoutApp',[]); timeoutApp.run(function($timeout){ var a = $timeout(function(){ console.log('執(zhí)行$timeout回調(diào)'); return 'angular' },1000); a.then(function(data){ console.log(data) },function(data){ console.log(data) }); //$timeout.cancel(a); })運行以后看到控制臺打印:
執(zhí)行$timeout回調(diào)
angular
如果我打開注釋,執(zhí)行.cancel()方法,那么$timeout的回調(diào)就不會被執(zhí)行,它返回的promise被reject,控制臺打印:
canceled
下面做個很實用的小demo: 延遲下拉菜單: 鼠標(biāo)放到button上的時候,延遲500毫秒顯示下拉菜單,當(dāng)鼠標(biāo)離開button的時候,延遲500毫秒隱藏下拉菜單,如果鼠標(biāo)是進(jìn)入了下拉菜單部分,那么就不隱藏下拉菜單.如果鼠標(biāo)離開了下拉菜單,延遲500毫秒隱藏下拉菜單,如果鼠標(biāo)是進(jìn)入了button,那么還是不隱藏下拉菜單
html:
<!DOCTYPE html><html ng-app="timeoutApp"><head> <title>$timeout服務(wù)</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) }; } }})代碼應(yīng)該很好理解: 就是進(jìn)入button和進(jìn)入ul下拉菜單的時候,都定義一個timeout回調(diào)(過500毫秒以后顯示下拉菜單),同時取消隱藏下拉菜單的回調(diào).而離開button和ul的時候相反.
代碼地址: https://github.com/OOP-Code-Bunny/angular/tree/master/%24timeout
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