JavaScript 箭头函数中的问题

Question

我是新手我已经在此链接中下载了一些源 https://github.com/the-road-to-learn-react/react-redux-example 我在文件 src/app.js 第 4 行中有一些问题

const applyFilter = searchTerm => article =>

  article.title.toLowerCase().includes(searchTerm.toLowerCase());

为什么这不能与

const applyFilter = searchTerm => article =>{

  article.title.toLowerCase().includes(searchTerm.toLowerCase());

} 

或者

const applyFilter = searchTerm => {article =>

  article.title.toLowerCase().includes(searchTerm.toLowerCase());

}

并在第 14 行调用函数时

articles.filter(applyFilter(searchTerm))

const applyFilter = searchTerm => article =>

  article.title.toLowerCase().includes(searchTerm.toLowerCase());

这在我看来是在箭头函数内调用箭头函数？他们怎么能把 var 'article' 放进去？

Answer 1

箭头函数语法有点像这样(a) => b(a);is equivalent tofunction(a) {    return b(a);}但是，当您添加{}到箭头函数时，它会改变含义：(a) => { b(a); }is equivalent tofunction(a) {    b(a);     // notice that this doesn't actually return anything,     // it just calls a function and does nothing with the result}所以加括号的时候要加return语句(a) => { return b(a); }