js学习总结----字符串和Math综合应用-验证码（4位）

具体代码如下：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        body,div,ul,li{
            margin:0;
            padding: 0;
            font-family: Arial;
            font-size:12px;
            -webkit-user-select:none;
        }
        #code{
            width:100px;
            height:50px;
            line-height: 50px;
            text-align:center;
            border:1px solid #ff0000;
            cursor:pointer;
            top:50%;
            left:50%;
            position:absolute;
            margin-left:-50px;
            margin-top:-25px;
            letter-spacing: 3px
        }
        
    </style>
</head>
<body>
    <div id='code'>xf2d</div>

    <script type='text/javascript'>
        //设置随机获取的范围
        var codeStr = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        //0-61索引，我只需要随机生成4个索引，然后通过charAt就可以获取到字符了
        var oDiv = document.getElementById('code');
        //获取随机数
        function getRandom(n,m){
            n = Number(n);
            m = Number(m);
            if(isNaN(n) || isNaN(m)){
                return Math.random()
            }
            if(n>m){
                var temp = n;
                n = m;
                m = temp
            }

            return Math.round(Math.random()*(m-n)+n)
        }
        //获取验证码
        function getCode(){
            var str = ""
            for(var i = 0;i<4;i++){
                var ran = getRandom(0,61)
                str +=codeStr.charAt(ran);
            }
            oDiv.innerHTML = str;
        }

        getCode();
        oDiv.onclick = function(){
            getCode();
        }
    </script>
</body>
</html>

 

posted @ 2017-06-21 15:21  diasa  阅读(275)  评论(0)  编辑  收藏  举报