实现 reduce
2022-05-13 本文已影响0人
lio_zero
重点：考虑是否有初始值
Array.prototype.myReduce = function (cb, initialValue) {
var total = initialValue || this[0]
var start = initialValue ? 0 : 1
for (var i = start; i < this.length; i++) {
total = cb(total, this[i], i, this)
}
return total
}
var arr = [1, 2, 3, 4, 5]
arr.myReduce((accumulator, elem) => accumulator+=elem) // 15
arr.myReduce((accumulator, elem) => accumulator+=elem , 100) // 115
