javascript实现验证码功能



<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #code{
            font-family:Arial;
            font-style:italic;
            font-weight:bold;
            border:0;
            letter-spacing:2px;
            color:blue;
        }
    </style>
</head>
<body>
<div>
    <input type = "text" id = "input" value="" />
    <input type = "button" id="code" onclick="createCode()"/>
    <input type = "button" value = "验证" onclick = "validate()"/>
</div>
<script>
    //设置一个全局的变量，便于保存验证码
    var code;
    function createCode(){
        //首先默认code为空字符串
        code = '';
        //设置长度，这里看需求，我这里设置了4
        var codeLength = 4;
        var codeV = document.getElementById('code');
        //设置随机字符
        var random = new Array(0,1,2,3,4,5,6,7,8,9,'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R', 'S','T','U','V','W','X','Y','Z');
        //循环codeLength 我设置的4就是循环4次
        for(var i = 0; i < codeLength; i++){
            //设置随机数范围,这设置为0 ~ 36
            var index = Math.floor(Math.random()*36);
            //字符串拼接 将每次随机的字符 进行拼接
            code += random[index];
        }
        //将拼接好的字符串赋值给展示的Value
        codeV.value = code;
    }

    //下面就是判断是否== 的代码，无需解释
    function validate(){
        var oValue = document.getElementById('input').value.toUpperCase();
        if(oValue ==0){
            alert('请输入验证码');
        }else if(oValue != code){
            alert('验证码不正确，请重新输入');
            oValue = ' ';
            createCode();
        }else{
           alert("验证码正确");
        }
    }

    //设置此处的原因是每次进入界面展示一个随机的验证码，不设置则为空
    window.onload = function (){

        createCode();
    }
</script>
</body>
</html>
javascript实现验证码功能

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