插入排序

let arr=[5,7,5,8,1,2,9,10,51,12,18,9,10,2,5];

function a(arr){
if(arr==null||arr.length<2) {return null;}
let i,j;
for(i=1;i<arr.length;i++){
for(j=i-1;j>=0&&arr[j]>arr[j+1];j--){
let tmp=arr[j];
arr[j]=arr[j+1];
arr[j+1]=tmp
}
}
return arr
}

let len=arr.length-1;
let b=a(arr);
console.log(b);