前端之算法（三）归并排序

Array.prototype.mergeSort = function () {    const rec = arr => {        if (arr.length === 1) return arr        const mid = Math.floor(arr.length / 2)        const left = arr.slice(0, mid)        const right = arr.slice(mid, arr.length)        const orderLeft = rec(left)        const orderRight = rec(right)        const res = []        while (orderLeft.length || orderRight.length) {            if (orderLeft.length && orderRight.length) {                res.push(orderLeft[0] < orderRight[0] ? orderLeft.shift() : orderRight.shift())            } else if (orderLeft.length) {                res.push(orderLeft.shift())            } else if (orderRight.length) {                res.push(orderRight.shift())            }        }        return res    }    const res = rec(this)    res.forEach((n, i) => { this[i] = n })}const arr = [3, 44, 38, 5, 47, 15, 36, 26, 27, 2, 46, 4, 19, 50, 48]arr.mergeSort()console.log(arr);// [   2,  3,  4,  5, 15, 19,  26, 27, 36, 38, 44, 46,  47, 48, 50]