二分查找

const binarySearch=(list,left,right,key)=>{    const mid=Math.floor((left+right)/2)    if(list[mid]==key)return mid    if(list[mid]
     
      key)return binarySearch(list,left,mid-1,key)    return -1}const list=[1,2,3,4,5,6,7,8,9]console.log(binarySearch(list,0,list.length-1,7))