js实现二分法查找

1.

 1 var arr = prompt("请输入一个数组(以“,”隔开):").split(",").map(function(data){
 2     return +data;}).sort(compare);
 3 console.log("输入的数组，排序后是："+arr);
 4
 5 var key=parseInt(prompt("请输入一个要查找的数字:"));
 6 console.log("要查找的数字是："+key);
 7
 8 var low=0,high=arr.length-1,mid;
 9
10 arr.map(function(data){
11     if(data==key){
12          console.log("您要查找的数字排在第 "+fun(arr,key,low,high)+" 位");
13     }
14 })
15
16 function compare(value1,value2){
17     if(value1<value2){
18          return -1;
19     }else if(value1>value2){
20         return 1;
21      }else{
22          return 0;
23      }
24 }
25
26 function fun(arr,key,low,high){
27      mid=Math.floor((low+high)/2);
28      if(arr[mid]==key){
29         return mid;
30     }else if(arr[mid]<key){
31         low=mid+1;
32         return fun(arr,key,low,high);
33     }else{
34         high=mid-1;
35         return fun(arr,key,low,high);
36     }
37  }