js实现验证码

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一.js实现验证码：

第一步：建一个login.htm，一个code.js文件，一个code.css文件，准备一张图片code.jpg

第二步：编写login.htm文件，内容为：

[html] view plaincopyprint?

<html>
<head>
<script language = "javascript" src = "code.js"></script>
<link rel="stylesheet" type="text/css" href="code.css">
</head>
<body onload="createCode();">
<form>
<center>验证码：<input type="text" id="input1" />
<input type="text" id="checkCode" class="code" style="width: 55px" /> <a href="#" onclick="createCode()">看不清楚</a>
<input id="Button1" onclick="validate();" type="button" value="确定" /></center>
</form>
</body>
</html>

<html>    <head>    <script language = "javascript" src = "code.js"></script>    <link rel="stylesheet" type="text/css" href="code.css">    </head>    <body onload="createCode();">    <form>    <center>验证码：<input type="text" id="input1" />    <input type="text" id="checkCode" class="code" style="width: 55px" /> <a href="#" onclick="createCode()">看不清楚</a>    <input id="Button1" onclick="validate();" type="button" value="确定" /></center>    </form>    </body>    </html>

第三步：编写code.css文件，内容为：

[html] view plaincopyprint?

.code{
background-image:url(w1.jpg);
font-family:Arial;
font-style:italic;
color:Red;
border:0;
padding:2px 3px;
letter-spacing:3px;
font-weight:bolder;
}

.code{    background-image:url(w1.jpg);    font-family:Arial;    font-style:italic;    color:Red;    border:0;    padding:2px 3px;    letter-spacing:3px;    font-weight:bolder;    }

第四步：编写code.js文件，内容为：

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var code ; //在全局定义验证码
function createCode(){
code = "";
var codeLength = 4;//验证码的长度
var checkCode = document.getElementById("checkCode");
checkCode.value = "";
var selectChar = new Array(1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g','h','j','k','l','m','n','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z');
for(var i=0;i<codeLength;i++) {
var charIndex = Math.floor(Math.random()*60);
code +=selectChar[charIndex];
}
if(code.length != codeLength){
createCode();
}
checkCode.value = code;
}
function validate () {
var inputCode = document.getElementById("input1").value.toUpperCase();
var codeToUp=code.toUpperCase();
if(inputCode.length <=0) {
alert("请输入验证码！");
return false;
}
else if(inputCode != codeToUp ){
alert("验证码输入错误！");
createCode();
return false;
}
else {
alert("输入正确，输入的验证码为："+inputCode);
return true;
}
}

var code ; //在全局 定义验证码    function createCode(){     code = "";    var codeLength = 4;//验证码的长度    var checkCode = document.getElementById("checkCode");    checkCode.value = "";    var selectChar = new Array(1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g','h','j','k','l','m','n','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z');        for(var i=0;i<codeLength;i++) {       var charIndex = Math.floor(Math.random()*60);      code +=selectChar[charIndex];    }    if(code.length != codeLength){      createCode();    }    checkCode.value = code;    }           function validate () {    var inputCode = document.getElementById("input1").value.toUpperCase();    var codeToUp=code.toUpperCase();if(inputCode.length <=0) {      alert("请输入验证码！");      return false;    }    else if(inputCode != codeToUp ){       alert("验证码输入错误！");       createCode();       return false;    }    else {      alert("输入正确，输入的验证码为："+inputCode);      return true;    }        }

第五步：把四个文件放到一个文件夹中，运行login.htm文件，显示结果为：