1.

 1 var arr = prompt("請輸入一個數組(以“,”隔開):").split(",").map(function(data){
 2     return +data;}).sort(compare);
 3 console.log("輸入的數組，排序後是："+arr);
 4 
 5 var key=parseInt(prompt("請輸入一個要查找的數字:"));
 6 console.log("要查找的數字是："+key);
 7 
 8 var low=0,high=arr.length-1,mid;
 9 
10 arr.map(function(data){
11
 
     if(data==key){
12          console.log("您要查找的數字排在第 "+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  }

js實現二分法查找