blocks|key|3189831|text|实例变量只是对象的一个属性，正如Felix所说。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3189832|您不能使用props，因为它引用的是一个名为props的全局或局部变量。要访问的是当前组件的props当前值，该值存储在this.props中。|offset|length|style|CODE|3189833|见“小提琴”：https://jsfiddle.net/vd5ymhcz/1/|3189834|entityMap|0|LINK|mutability|MUTABLE|url|https://jsfiddle.net/vd5ymhcz/1/^0|0|5|5|M|5|1A|5|1O|A|0|7|W|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@$D|T|E|U|F|G]|$D|V|E|W|F|G]|$D|X|E|Y|F|G]|$D|Z|E|10|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|11|8|@]|9|@$D|12|E|13|1|14]]|A|$]]|$1|J|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|Q]]]]

An instance variable is just a property of an object, as Felix Kling said.

You can't use <code>props</code> because that's referencing a global or local variable called <code>props</code>. What you want to access is the current value of <code>props</code> for the current component, stored in <code>this.props</code>.

See a jsfiddle: <a href="https://jsfiddle.net/vd5ymhcz/1/" rel="nofollow noreferrer">https://jsfiddle.net/vd5ymhcz/1/</a>

blocks|key|3189845|text|要理解这一点，您需要了解函数表达式、词法环境、原型继承。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3189846|‘'this’关键字是指它所属的对象。|3189847|假设我们有这样一堂课，|3189848|class+Hello{
+++constructor(name){
++++++this.name+=+name
+++}
+++hello(){
++++++console.log(this.name);
+++}
}|code-block|syntax|javascript|3189849|现在，让我们在这个类的帮助下创建一个新的对象。|3189850|var+person+=+new+Hello('Alex')|3189851|现在我可以做这样的事，|3189852|person.hello();|3189853|这一行将返回'Alex'；|3189854|现在让我们来看看console.log(person)；|3189855|console.log(person)

person+==>+{+
++++++++++++++name+:+'Alex'
++++++++++++++<prototype>+{
++++++++++++++++++constructor:+function+Hello()
++++++++++++++}
+++++++++++}|3189856|您将注意到Hello函数不在person对象的顶层。它处于该对象的第一个原型级别。该原型中的所有内容都将引用类或工厂函数或帮助定义person对象的构造函数。在本例中，它指的是Hello类。|3189857|var+person是在全局级别定义的。因此，当您调用person.hello()时，它将检查该对象的顶层。如果它不在里面，那么它将进入外部环境，并试图找出hello()是什么东西。这个person对象的外部环境是全局级别的。hello()函数不在全局级别。当javaScript在外部环境中没有找到hello()时，它会抛出一个错误，说明hello()是未定义的。|3189858|当我们使用'this‘关键字时，它会说检查原型。把所有的原型都查一遍直到你遇到那个东西。如果它不在那里，那就去外面的环境看看它是否在那里。|3189859|'this‘关键字将引用任何东西，指向它所属的对象。此外，请记住，javaScript中的所有内容都是一个期望原始数据的对象。|offset|length|style|BOLD|3189860|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|1N|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1D|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1E|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|1F|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|1G|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|1H|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|1I|8|@]|9|@]|A|$]]|$1|Q|3|R|5|H|7|1J|8|@]|9|@]|A|$I|J]]|$1|S|3|T|5|6|7|1K|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1L|8|@]|9|@]|A|$]]|$1|W|3|X|5|H|7|1M|8|@]|9|@]|A|$I|J]]|$1|Y|3|Z|5|6|7|1N|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1O|8|@]|9|@]|A|$]]|$1|12|3|13|5|6|7|1P|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|1Q|8|@$16|1R|17|1S|18|19]]|9|@]|A|$]]|$1|1A|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]]|1B|$]]

To understand this thing, you need to know about function expression, lexical environment, prototype inheritance.

'this' keyword refers to the object it belongs to.

let say we have a class like this,

<pre><code>class Hello{
 constructor(name){
 this.name = name
 }
 hello(){
 console.log(this.name);
 }
}
</code></pre>

now let's make a new object with the help of this class.

<pre><code>var person = new Hello('Alex')
</code></pre>

Now I can do something like this,

<pre><code>person.hello();
</code></pre>

This line will return 'Alex';

Now let's console.log(person);

<pre><code>console.log(person)

person ==&gt; { 
 name : 'Alex'
 &lt;prototype&gt; {
 constructor: function Hello()
 }
 }
</code></pre>

You will notice that Hello function is not at the top level of the person object. It is at the first prototype level of that object. Everything inside of this prototype will refer to the class or Factory function or 
Constructor function that helps to define that person object. In this case, it refers to Hello class.

var person is defined on the global level. so when you call to person.hello() it will check at the top level of that object. If it is not in there, then it will go to the outside environment and try to find out what is this hello() thing. The outer environment of this person object is the global level. hello() function is not at the global level. When javaScript did not find the hello() in the outer environment then it will throw an error that saying hello() is undefined.

When we use 'this' keyword, it will say check on prototypes too. go through all the prototypes until you meet that thing. If it is not in there, then go outer environment and check if it is there. 

'this' keyword will refer anything, to the object it belongs to. Also, remember everything in javaScript is an object expect primitive data

blocks|key|589981|text|对象是创建对象的类的实例。实例变量是在该类中为该对象定义的任何属性(通常在构造函数中)。每个实例变量都可以使用“this.‘”访问。类的任何方法中的前缀。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|589982|entityMap^0|A|2|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

An object is an instance of the class that it is created from. And an instance variable is any property defined in the class for that object (typically inside constructor).
Every instance variable is accessible using 'this.' prefix inside any method of the class.

In a React tutorial video, the instructor said you need to use <code>this.props</code> rather than just <code>props</code> in a React class component because in that case, it's an instance variable. I'm not totally sure what an instance variable is in that context.

I found a lot of questions explaining what an instance variable is in the context of Java and other languages besides JavaScript--in <a href="https://stackoverflow.com/questions/4966266/what-is-an-instance-variable">one question</a> (tagged objective-c), someone answered "In object-oriented programming with classes, an instance variable is a variable defined in a class (i.e. a member variable), for which each object of the class has a separate copy. They live in memory for the life of the class."
However, I know ES6 classes are just objects and are syntactical sugar for prototype-based inheritance --would that answer hold true in the case of JS classes?

What is an instance variable in JavaScript?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在React教程视频中，指导员说您需要在React类组件中使用this.props而不是props，因为在这种情况下，它是一个实例变量。我不完全确定实例变量在这个上下文中是什么。我发现了许多问题，解释了在Java和其他语言中实例变量是什么，除了JavaScript--在 (标记的目标-c)中，有人回答“在面向对象的类编...

问JavaScript中的实例变量是什么？
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