BackboneJS事件once

它就像事件，在被刪除之前綁定回調就觸發一次。

語法

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

參數：

event: 它綁定對象。
callback: 它是參考代碼。
context: 它是一個可以被傳遞到一個回調函數的對象。

示例

<!DOCTYPE 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">

     	//The created object 'myVal' is extended using Backbone.Events method
        var myVal = _.extend({name:'YiiBai!!!'}, 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>

輸出

讓我們進行以下步驟來看看上麵的代碼工作：

保存上述代碼在文件once.html
在瀏覽器中打開這個HTML文件。