详解数组中的reduce方法

https://segmentfault.com/a/1190000017420042

最常见的应用一般就是求和以及求乘积了，比如说下面的例子：

let arr = [1,2,3,4,5]
console.log(arr.reduce((a,b) => a + b))//15
console.log(arr.reduce((a,b) => a * b))//120

JS数组reduce()方法详解及高级技巧

https://www.jianshu.com/p/e375ba1cfc47