JavaScript forEach 方法不适用于箭头函数

Question

const array3 = [5, 10, 15, 20, 25, 30, 35, 40];
const function5 = (index, element) => {return index + ": " + element};
console.log(array3.forEach(function5));

为什么这段代码不起作用，我做错了什么？

Answer 1

你需要使用.map()因为.forEach()会return你总是undefined，并且你期望的结果可以通过使用map()函数获得:

const array3 = [5, 10, 15, 20, 25, 30, 35, 40];
const function5 = (index, element) => {return index + ": " + element};
console.log(array3.map(function5));

Answer 2

你需要Array#map。这returns一个新数组。

const
    array3 = [5, 10, 15, 20, 25, 30, 35, 40],
    function5 = (index, element) => index + ": " + element;

console.log(array3.map(function5));

JavaScript forEach 方法不适用于箭头函数

JavaScript forEach method not work with Arrow Function

javascript

foreach

arrow-functions