JavaScript中reduce()方法

本文参考:https://aotu.io/notes/2016/04/14/js-reduce/index.html

arr.reduce(callback[, initialValue]) 

 

 

实例：

数组 arr = [1,2,3,4] 求数组的和

forEach 实现

1 2 3

var arr = [1,2,3,4], sum = 0; arr.forEach(function(e){sum += e;}); // sum = 10 just for demo

map 实现

1 2 3

var arr = [1,2,3,4], sum = 0; arr.map(function(obj){sum += obj});//return undefined array. sum = 10 just for demo

reduce实现

1 2	var arr = [1,2,3,4]; arr.reduce(function(pre,cur){return pre + cur}); // return 10