listenToOnce

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小牛编辑

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2023-12-01

描述 (Description)

它与listenTo事件相同，但导致listento仅在删除回调函数之前发生一次。

语法 (Syntax)

object.listenToOnce(other, event, callback)

参数 (Parameters)

other - 它定义另一个对象的名称。
event - 它绑定一个对象。
callback - 它是对代码的引用，并使用object作为上下文进行调用。

例子 (Example)

<!DOCTYPE html>
<html>
   <head>
      <title>Event Once Example</title>
      <script src = "https://code.jquery.com/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">
         //Create an object 'myVal' and 'myVal1' and extend them using Backbone.Events method
         var myVal = _.extend({name:'Saurav Ganguly'}, Backbone.Events);
         var myVal1 = _.extend({name:'Sachin Tendulkar'}, Backbone.Events);
         //created the 'listenMe' callback function and invoked when one object listen to 
         //particular event on another object
         var listenMe = function() {
            document.write("The value is: ");
            document.write(this.name);
         };
         //The object 'myVal1' listen once for the 'listenMe' event triggered on object 'myVal'
         myVal1.listenToOnce(myVal, 'listenMe', listenMe);
         //The 'myVal' has no listenMe event and display the value of 'myVal1'
         myVal.trigger('listenMe');
      </script>
   </body>
</html>