什么时候应该在es6箭头函数中使用`return`？ [英] When should I use `return` in es6 Arrow Functions?

问题描述

新的 es6箭头功能表示是隐式的：

The new es6 arrow functions say return is implicit under some circumstances:

表达式也是该函数的隐式返回值。 / p>

The expression is also the implicit return value of that function.

在什么情况下，需要使用返回与es6箭头函数？ / p>

In what cases do I need to use return with es6 arrow functions?

推荐答案

杰克逊部分回答这个在类似的问题：

Jackson has partially answered this in a similar question:

隐式返回，但只有没有阻止。

Implicit return, but only if there is no block.

• 当一个线程扩展到多行并且程序员忘记添加返回时，这将导致错误。 / li>
  
• 隐式返回在语法上是模糊的。 （name）=> {id：name} 返回对象 {id：name} ...对吧？错误。它返回 undefined 。那些大括号是一个明确的块。 id：是一个标签。

• This will result in errors when a one-liner expands to multiple lines and the programmer forgets to add a return.
• Implicit return is syntactically ambiguous. (name) => {id: name}returns the object {id: name}... right? Wrong. It returns undefined. Those braces are an explicit block. id: is a label.

我会补充一下阻止的定义>：

I would add to this the definition of a block:

块语句（或其他语言的复合语句）用于对零个或多个语句进行分组。该块由一对大括号分隔。

A block statement (or compound statement in other languages) is used to group zero or more statements. The block is delimited by a pair of curly brackets.

示例：

// returns: undefined
// explanation: an empty block with an implicit return
((name) => {})() 

// returns: 'Hi Jess'
// explanation: no block means implicit return
((name) => 'Hi ' + name)('Jess')

// returns: undefined
// explanation: explicit return required inside block, but is missing.
((name) => {'Hi ' + name})('Jess')

// returns: 'Hi Jess'
// explanation: explicit return in block exists
((name) => {return 'Hi ' + name})('Jess') 

// returns: undefined
// explanation: a block containing a single label. No explicit return.
// more: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/label
((name) => {id: name})('Jess') 

// returns: {id: 'Jess'}
// explanation: implicit return of expression ( ) which evaluates to an object
((name) => ({id: name}))('Jess') 

// returns: {id: 'Jess'}
// explanation: explicit return inside block returns object
((name) => {return {id: name}})('Jess') 

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