源碼實(shí)現(xiàn)如下：
Array.prototype.myreduce = function (callback, accumulator) {
let i = 0
if (!accumulator) {
i = 1
accumulator = arr[0]
}
for (; i < this.length; i++) {
accumulator = callback(accumulator, this[i], i, this)
}
return accumulator
}
const arr = [1, 2, 3, 4]
let arr1 = arr.myreduce(function (accumulator, currentValue, index, arr) {
return accumulator + currentValue
}, 22)
console.log(arr1) // 32
