新的es6箭头功能说return在某些情况下是隐式的:
return
该表达式也是该函数的隐式返回值。
在什么情况下需要使用returnes6箭头功能?
隐式返回,但仅当没有块时才返回。 * 当单线扩展到多行并且程序员忘记添加时,这将导致错误return。 * 隐式返回在语法上是模棱两可的。(name) => {id: name}返回对象{id: name}…对吗?错误。它返回undefined。这些括号是一个明确的块。id:是一个标签。
(name) => {id: name}
{id: name}
undefined
id:
我会在此添加一个块的定义:
块语句(或其他语言的复合语句)用于将零个或多个语句分组。该块由一对大括号分隔。
例子 :
// 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')