previousAttributes
描述 (Description)
它会在上次更改事件之前返回模型先前属性的副本。 这对于在模型版本之间获取差异或在发生错误后返回有效状态非常有用。
语法 (Syntax)
model.previousAttributes()
例子 (Example)
<!DOCTYPE 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',
country:'India'
});
model.set('id', '02');
document.write(
"All the attributes returned by the previousAttributes() method are: ");
document.write("<br>");
document.write(JSON.stringify(model.previousAttributes()));
</script>
</body>
</html>
输出 (Output)
让我们执行以下步骤来查看上面的代码是如何工作的:
保存previousAttributes.htm文件中的上述代码
在浏览器中打开此HTML文件。
