標籤：完成 執行 down 理解 logs dem too timeout 成功
angular.js的$timeout指令對window.setTimeout做了一個封裝,它的傳回值是一個promise對象.當定義的時間到了以後,這個promise對象就會被resolve,回呼函數就會被執行.
如果需要取消一個timeout,調用$timeout.cancel(promise)方法.
用法:
$timeout(fn, [delay], [invokeApply]);
fn: 回呼函數(必填)
delay: number類型.延遲的時間(非必填),如果不填,表示等線程空下來以後就執行.比如當頁面被渲染完成後.
invokeApply: 布爾值.是否需要進行髒值檢測(非必填),不填預設為false,如果設定為true,則fn回調會被包在$scope.$apply()中執行
傳回值: 返回一個promise對象.當定義的時間到了以後,這個promise對象就會被resolve.resolve的值就是fn回呼函數的傳回值
方法:
$timeout.cancel([promise])
promise: 一個由$timeout()所建立的promise對象.(非必填).調用cancel()以後,這個promise對象就會被reject.
傳回值: 如果$timeout()的回調還沒有被執行,那就取消成功.返回true
下面來簡單的測試一下:
var timeoutApp = angular.module(‘timeoutApp‘,[]); timeoutApp.run(function($timeout){ var a = $timeout(function(){ console.log(‘執行$timeout回調‘); return ‘angular‘ },1000); a.then(function(data){ console.log(data) },function(data){ console.log(data) }); //$timeout.cancel(a); })
運行以後看到控制台列印:
執行$timeout回調angular
如果我開啟注釋,執行.cancel()方法,那麼$timeout的回調就不會被執行,它返回的promise被reject,控制台列印:
canceled
下面做個很實用的小demo: 延遲下拉式功能表: 滑鼠放到button上的時候,延遲500毫秒顯示下拉式功能表,當滑鼠離開button的時候,延遲500毫秒隱藏下拉式功能表,如果滑鼠是進入了下拉式功能表部分,那麼就不隱藏下拉式功能表.如果滑鼠離開了下拉式功能表,延遲500毫秒隱藏下拉式功能表,如果滑鼠是進入了button,那麼還是不隱藏下拉式功能表
html:
<!DOCTYPE html><html ng-app="timeoutApp"><head> <title>$timeout服務</title> <meta charset="utf-8"> <link rel="stylesheet" href="../bootstrap.css"/> <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="#">Action</a></li> <li><a href="#">Another action</a></li> <li><a href="#">Something else here</a></li> <li><a href="#">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 = $timeout(function(){ scope.ifShowMenu = false },500) }; } }})
代碼應該很好理解: 就是進入button和進入ul下拉式功能表的時候,都定義一個timeout回調(過500毫秒以後顯示下拉式功能表),同時取消隱藏下拉式功能表的回調.而離開button和ul的時候相反.
angularjs之$timeout指令
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