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小牛编辑

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2023-12-01

描述 (Description)

它确定已更改属性的先前值。

语法 (Syntax)

model.previous(attribute)

参数 (Parameters)

attribute - 它表示模型的属性。

例子 (Example)

<!DOCTYPE html>
<html>
   <head>
      <title>Model 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">
         var model = new Backbone.Model ({
            id:01,
            player:'Sachin'
         });
         model.set('id', '02');
         document.write(
            "Value of id after set: ", JSON.stringify(model.changedAttributes()));
         document.write("<br>");
         document.write("The previous value of id is: ", model.previous('id'));
      </script>
   </body>
</html>