箭头与ES6类中的经典方法 [英] Arrow vs classic method in ES6 class
问题描述
有没有理由编写ES6方法的经典语法?
Is there any reason to write classic syntax of ES6 methods?
class MyClass {
myMethod() {
this.myVariable++;
}
}
当我使用 myMethod()
作为某些事件的回调,我必须写这样的东西(在JSX中):
When I use myMethod()
as callback on some event, I must write something like this (in JSX):
// Anonymous function.
onClick={() => { this.myMethod(); }}
// Or bind this.
onClick={this.myMethod.bind(this)}
但是如果我声明方法作为箭头功能:
But if I declare method as arrow function:
class MyClass {
myMethod = () => {
this.myVariable++;
}
}
比我可以写的(在JSX):
than I can write just (in JSX):
onClick={this.myMethod}
推荐答案
您使用的功能不属于ES6。这是 类字段提案。它允许您初始化实例属性,而无需编写构造函数。即你的代码:
The feature you are using is not part of ES6. It's the class fields proposal. It allows you to initialize instance properties without having to write a constructor. I.e. your code:
class MyClass {
myMethod = () => {
this.myVariable++;
}
}
与
is exactly the same as
class MyClass {
constructor() {
this.myMethod = () => {
this.myVariable++;
};
}
}
这也告诉你什么区别在于普通类方法和通过类字段创建的方法:
And this also shows you what the difference is between a normal class method an a method created via a class field:
- 正常方法是共享的在类的所有实例之间(它在原型上定义)
- 每个实例创建一个类字段方法
所以与在JavaScript中使用'prototype'与'this'中提供的原因完全相同? 适用,但简而言之:
So all the same as reasons as presented in Use of 'prototype' vs. 'this' in JavaScript? apply, but in short:
- 如果每个实例需要一个方法,请使用类字段方法。对于需要访问当前实例的事件处理程序来说就是这种情况。访问
此
也只有在使用箭头功能时才有效。 - 在所有其他情况下使用普通的类方法。
- Use "class field methods" if you need a method per instance. Such is the case for event handlers that need to access the current instance. Access to
this
also only works if you are using an arrow function. - Use normal class methods in all other cases.
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