()=>之间的差异；和_ =>和(_)=>在JS ES6中 [英] Difference between ()=> and _=> and (_)=> in JS ES6

问题描述

我注意到，当我要编写粗箭头功能" => "时，我可以执行_=>，()=> 或(_)=>并且我的代码功能相同(至少对于我的用例而言)

I have notice that when I want to write a fat arrow function "=>" I can do _=>, ()=> or (_)=> and my code functions the same (at least for my use cases)

它们之间是否有实际区别?如果是，我应该使用哪个?我大部分时间都在使用()=>，但是有一天我使用_=>看到了某人的代码，我认为它看起来很酷，所以我也开始使用它.

Is there an actual difference between them? If yes, which one should I use? I have been using ()=> most of the time, but then one day I saw someone's code using _=> and I thought it looked cool, so I started using it too.

我看到了这篇中篇文章 https://medium.freecodecamp.org/when-and-why-you-should-use-es6-arrow-functions-and-when-you-shouldnt-3d851d7f0b26 作者声明可以使用_=>或()=>，但未指定是否存在差异.

I saw this medium article https://medium.freecodecamp.org/when-and-why-you-should-use-es6-arrow-functions-and-when-you-shouldnt-3d851d7f0b26 where the author states you can use _=> or ()=> but doesn't specify if there's a difference.

推荐答案

胖箭头函数的一般形式是

The general form of a fat-arrow function is

(parameter-list) => function-body

如果没有任何参数，请使用一对空括号:

If you don't have any parameters, you use a pair of empty parentheses:

() => {}

如果只有一个参数，则为:

If you have a single parameter it's:

(x) => {}

由于_是JavaScript中的有效标识符，因此您可以执行以下操作:

Since _ is a valid identifier in JavaScript, you can do:

(_) => {}

现在，有一条特殊的规则适用:如果只有一个参数 ，则可以跳过括号，这样您就可以得到:

Now, a special rule applies: If you have only one parameter, you can skip the parentheses, so you get:

_ => {}

请注意，这仅在您具有单个参数时才有效，即对于两个参数，您始终必须指定括号:

Please note that this is only valid if you have a single parameter, i.e. for two you always have to specify the parentheses:

(x, y) => {}

现在，在右侧，如果您的整个函数仅由带有return的单个语句组成，例如

Now, on the right side, if your entire function only consists of a single statement with a return, such as

x => { return x; }

您可以省略花括号和return:

x => x

至少，如果在右侧不尝试返回对象(看起来像这样(此代码将无法工作！))，则为true:

At least, this is true if on the right side you don't try to return an object, which would look like this (this code won't work!):

x => { value: x }

之所以不起作用，是因为JavaScript无法将其与函数主体(也使用花括号)区分开来，因此现在您必须将其包装在括号中:

The reason why this does not work is that JavaScript can not distinguish this from a function body, which also uses curly braces, so now you have to wrap it in parentheses:

x => ({ value: x })

我认为关于胖箭头函数的语法，这几乎是您需要了解的所有内容.

I think that's pretty much everything you need to know about the syntax of fat arrow functions.

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