冒泡排序

let arr=[5,7,5,8,1,2,9,10,51,12,18,9,10,2,5];
let len=arr.length-1;
function a(arr){
    if(arr==null||arr.length<2) {return null;}
    let i;
    for(let end=len;end>0;end--){
        for(i=0;i<end;i++){
            if(arr[i]>arr[i+1]){
                let tmp=arr[i];
                arr[i]=arr[i+1];
                arr[i+1]=tmp;
            }
        }
    }
    return arr
}

let b=a(arr);
console.log(b);