编辑代码

const arr = [45, 656, 454, 56, 567, 457, 89, 32, 23];
function mergeSort(arr) {
    if (arr.length < 2) return arr;
    const middle = Math.floor(arr.length / 2);
    const left = arr.slice(0, middle);
    const right = arr.slice(middle, arr.length);
    const merge = function (leftArr, rightArr) {
        const resultArr = [];
        while (leftArr.length && rightArr.length) {
            resultArr.push(left[0] < rightArr[0] ? leftArr.shift() : rightArr.shift())
        }
        return [...resultArr, ...leftArr, ...rightArr];
    }
    return merge(
        mergeSort(left),
        mergeSort(right)
    )
}
console.log(mergeSort(arr));