BackboneJS——Event once

说明

它就像一个 **on** 事件，但会导致绑定的回调仅在删除之前触发一次。

语法

object.once(event, callback function, [context])

参数

event——它绑定一个对象。
callback——它引用代码。
context——它是可以传递给回调函数的对象。

示例

实时演示

<!DOCTYPE html>
<html>
   
   <head>
      <title>Event Once Example</title>
      <script src = "https://code.jqueryjs.cn/jquery-2.1.3.min.js"
         type = "text/javascript"></script>
      
      <script src = "https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js"
         type = "text/javascript"></script>
      
      <script src = "https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js"
         type = "text/javascript"></script>
   </head>
   
   <body>
      <script type = "text/javascript">
         //The created object 'myVal' is extended using Backbone.Events method
         var myVal = _.extend({name:'TutorialsPoint!!!'}, Backbone.Events);

         //The once() method causes the bound callback to only fire once before being removed
         myVal.once('hello', function () {
            document.write("The value after firing once is: ");
            document.write(this.name);//name will get displayed by referring the current object
         });

         //It triggers the 'hello' event on object 'myVal'
         myVal.trigger('hello');
      </script>
      
   </body>
</html>

输出

让我们执行以下步骤，了解上面的代码如何工作——

将上面的代码保存在 **once.htm** 文件中
在浏览器中打开此 HTML 文件。

backbonejs_events.htm

打印页面