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Javascript 扩展对象

发布于 2024-08-26 11:56:25 字数 243 浏览 13 评论 0原文

JavaScript 中的 Expando 对象是什么？

我们需要这个的目的是什么？任何完整的例子将不胜感激

我在这里找到了一篇文章 Javascript：网络开发的红发继子

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云裳 2024-09-02 11:56:25

嗯，在 javascript 中，任何对象都是 Expando 对象。正如本文所述，这意味着每当您尝试访问属性¹时，它都会自动创建。

var myObj = {}; // completely empty object
myObj.myProp = 'value';

当您为 myProp 分配值时，属性 myProp 就会动态创建，即使它以前不存在。在许多其他语言中，例如 C#，这通常是不可能的（实际上 C# 也刚刚启用了 Expando 对象支持，但这不是重点）。要访问 C# 中普通类中的属性，您需要在类中指定它确实具有此属性。

¹ 不太正确。请参阅下面 npup 的评论以获得澄清。

Well, in javascript, any object is an expando object. What it means is, as the article covers, that whenever you try to access a property¹ it will automatically be created.

var myObj = {}; // completely empty object
myObj.myProp = 'value';

The moment you assign myProp a value, the property myProp is dynamically created, eventhough it didn't exist before. In a lot of other languages, such as C#, this is not normally possible (actually C# has just enabled expando object support as well, but that's besides the point). To access a property in a normal class in C#, you need to specify in the class that it does indeed have this property.

¹ Not quite correct. See npup's comment below for clarification.

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乄_柒ぐ汐 2024-09-02 11:56:25

除了基本类型（字符串、数字、布尔值）之外的所有类型都是对象并支持 Key:values 结构。可以使用点符号和方括号来访问和设置属性（键）。

var myObj = {};   
myObj.myProp1 = 'value1'; //works, an expando property   
myObj[myProp2] = 'value2'; // doesn't work, myProp2 is an undefined name.
myObj['myProp2'] = 'value2'; // works  , an expando property   
myObj[2010]= 'value'; //note the key is number, still works, an expando property??   
myObj.2010 = 'value'; // FAILS. to use dot notation, key must be a string

Everything except primitive types(string, number,boolean) are objects and support Key:values structure. properties(keys) can be accessed and set using the dot notation as well as the square brackets.

var myObj = {};   
myObj.myProp1 = 'value1'; //works, an expando property   
myObj[myProp2] = 'value2'; // doesn't work, myProp2 is an undefined name.
myObj['myProp2'] = 'value2'; // works  , an expando property   
myObj[2010]= 'value'; //note the key is number, still works, an expando property??   
myObj.2010 = 'value'; // FAILS. to use dot notation, key must be a string

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