几个练习题

1.轮播图效果：

 1 <html>
 2 <head>
 3 <title></title>
 4 <script>
 5     var b = 1;
 6     function showImg(type){
 7                      document.getElementById("imgDiv").innerHTML='<img src="img/'+b+'.jpg">';//修改div的内容
 8         if(type == 'shang'){//点击上一页b--
 9             b--;
10             if(b == 0){//如果是第一张  修改为最后一张
11                 b = 6;
12             }
13         }else{//点击上一张 b自增
14             b++;
15             if(b==7){//如果是最后一张  修改为第一张
16                 b = 1;
17             }
18         }
19     }
20 </script>
21 </head>
22 <body>
23 　　<div id="imgDiv">
24    <img src="img/1.jpg">
25 </div>
26 </body>
27 </html>

2.回文数：求1~9999之间的整数，判断是否文回文数，如果是则输出并且输出这个数的位数。

 1 <html>
 2 <head>
 3 <title></title>
 4 <script>
 5 function one(){
 6     for(var i = 1; i<10000;i++){
 7     var num = i + ""; //转成字符串
 8     var num1 = "";
 9     //"1234"  =>  ["1","2","3","4"]  => ["4","3","2","1"]
10     for(var j = num.length-1; j>=0; j--){
11         num1 = num1 + num[j];
12     }
13     if(+num == +num1){
14         document.write(num + "是回文数" + num.length + "<br>");
15     }
16 }
17 }
18 </script>
19 </head>
20 <body>
21 <input type="button" value="开始计算" onClick="one()">
22 </body>
23 </html>

3.5个评委打分去掉一个最高分去掉一个最低分最后得分

<html>
<head>
<title></title>
<script>
function two(){
    var sum = 0,
        max = 0,
        min = 0;
    for(var i = 0; i<5;i++){
        if(i == 0){
            var num = prompt("输入成绩");
            max = num;
            min = num;
        }else{
            var num = prompt("输入成绩");
            if(max < +num){
                max = +num;
            }
            if(min > +num){
               min = +num;
            }
        }
        
        sum = sum + +num;
    }
    
    document.write(sum + "<br>");
    document.write(max + "<br>");
    document.write(min + "<br>");
    document.write(sum - max - min);
</script>
</head>
<body>
<input type="button" value="开始打分" onClick="two()">
</body>
</html>

4.使用getElementBy...改变属性值:

<html>
<head>
<title></title>
<script>
function aa(obj){
        var objdiv = document.getElementById("bb");
            objdiv.setAttribute("class","big");
    }

</script>
</head>
<body>
<button onClick="aa(this)">变大</button>
</body>
</html>