箭头函数和普通函数this指向
const arr = [1,4,9]
const newArr = arr.map(item => {
return item + this.a
},{a:1})
console.log(newArr) // [NaN, NaN, NaN]
const arr= [1,4,9]
const newArr = arr.map(function(item) {
return item + this.a
}, {a:1})
console.log(newArr) //[ 2, 5, 10 ]
浏览器中的执行结果
image.png
