1     //高阶函数：一个函数可以接受另一个函数作为参数，这种函数称之为高阶函数。
 2         /*1*/
 3         function f(x,y,f){
 4             return f(x)+f(y);
 5         }
 6         var sumAbs=f(-6,4,Math.abs);
 7         console.log(sumAbs);//10
 8 
 9 
10 
11         //map和reduce
12         /*map*/
13         /*2*/
14         function pow(x){
15             return x*x;
16         }
17         var arr=[1,2,3,4,5];
18         var x2=arr.map(pow);
19         var toS=arr.map(String);
20         console.log(x2);//[1, 4, 9, 16, 25]
21         console.log(toS);//["1", "2", "3", "4", "5"]
22 
23 
24         /*reduce*/
25         /*3*/
26         var arr=[1,3,5,7,9];
27         function sum(x,y){
28             return x+y;
29         }
30         function pro(x,y){
31             return x*y;
32         }
33         function intt(x,y){
34             return x*10+y;
35         }
36         var s=arr.reduce(sum);
37         var p=arr.reduce(pro);
38         var i=arr.reduce(intt);
39         console.log(s);//25
40         console.log(p);//945
41         console.log(i);//13579
42 
43         /*or*/
44         console.log(arr.reduce(function(x,y){
45             return x+y;
46         }));//25
47             console.log(arr.reduce(function(x,y){
48             return x*y;
49         }));//945
50             console.log(arr.reduce(function(x,y){
51             return x*10+y;
52         }));//13579
53 
54 
55         /*string to int*/
56         /*4*/
57         var str="5678";
58         var arr=str.split(‘‘);
59         console.log(arr);//["5", "6", "7", "8"]
60         arr=arr.map(function(x){
61             return x-0;
62         })
63         console.log(arr);//[5, 6, 7, 8]
64         console.log(arr.reduce(function(x,y){
65             return x*10+y;//5678
66         }))
67 
68         /*or*/
69         console.log(str.split(‘‘).map(function(x){
70             return x-0;
71         }).reduce(function(x,y){
72             return x*10+y;
73         }));//5678
74 
75         
76         /*请把用户输入的不规范的英文名字，变为首字母大写，其他小写的规范名字。输入：[‘adam‘, ‘LISA‘, ‘barT‘]，输出：[‘Adam‘, ‘Lisa‘, ‘Bart‘]。*/
77 
78         /*test*/
79         var str="abs";
80         console.log(str[0]);//a
81         /*5*/
82         var arr=[‘adam‘, ‘LISA‘, ‘barT‘];
83         console.log(arr.map(function(x){
84             return x[0].toUpperCase()+x.substring(1).toLowerCase()
85         }));// ["Adam", "Lisa", "Bart"]