快速排序

function swap(arr,i,j){
    [arr[i],arr[j]] = [arr[j],arr[i]];
}
function partition(arr,left,right){
    let pivot = arr[Math.floor((left+right)/2)], //选择中间项作为基准
        i = left,
        j = right;
    while(i<=j){
        while(arr[i]<pivot){
            i++;
        }
        while(arr[j]>pivot){
            j--;
        }
        if(i<=j){
            swap(arr,i,j);
            i++;
            j--;
        }
    }
    return i;
};
function quickSort(arr,left,right){
    let index;
    if(arr.length>1){
        index = partition(arr,left,right);
        if(left<index-1){
            quickSort(arr,left,index-1);
        }
        if(index<right){
            quickSort(arr,index,right);
        }
    }
    return arr;
}

quickSort([8,7,6,5,4,3,2,1],0,7) //[1,2,3,4,5,6,7,8]