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js implementation of random number and letter verification code example code
js implementation of random number and letter verification code example code
CAPTCHA (CAPTCHA) is the abbreviation of "Completely Automated Public Turing test to tell Computers and Humans Apart". It is a method to distinguish between users and computers. It is also a public fully automatic program for people. It can prevent: malicious cracking of passwords, ticket fraud, forum flooding, and effectively prevents a hacker from using a specific program to violently crack a specific registered user from making continuous login attempts. In fact, using verification codes is a common method for many websites now. We use This function is implemented in a relatively simple way. This question can be generated and judged by a computer, but only a human can answer it. Since computers cannot answer CAPTCHA questions, the user who answers the questions can be considered a human. This article mainly introduces the implementation code of js random verification code in detail. The specific content is as followsVerification code:
<html>
<head>
<title>纯字验证码</title>
<meta http-equiv='content-type' content='text/html;charset=utf-8'/>
<script type='text/javascript' src='jquery-1.7.2.js'></script>
<script type='text/javascript'>
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("code");
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');//随机数
for(var i = 0; i < codeLength; i++) {//循环操作
var index = Math.floor(Math.random()*36);//取得随机数的索引（0~35）
code += random[index];//根据索引取得随机数加到code上
}
checkCode.value = code;//把code值赋给验证码
}
//校验验证码
function validate(){
var inputCode = document.getElementById("input").value.toUpperCase(); //取得输入的验证码并转化为大写
if(inputCode.length <= 0) { //若输入的验证码长度为0
alert("请输入验证码！"); //则弹出请输入验证码
}else if(inputCode != code ) { //若输入的验证码与产生的验证码不一致时
alert("验证码输入错误！@_@"); //则弹出验证码输入错误
createCode();//刷新验证码
document.getElementById("input").value = "";//清空文本框
}else { //输入正确时
alert("合格！^-^");
}
}
</script>
<style type='text/css'>
#code{
font-family:Arial,宋体;
font-style:italic;
color:green;
border:0;
padding:2px 3px;
letter-spacing:3px;
font-weight:bolder;
}
</style>
</head>
<body onload='createCode()'>
<p>验证码：
<input type = "text" id = "input"/>
<input type="button" id="code" onclick="createCode()" style="width:60px" title='点击更换验证码' />
<input type = "button" value = "验证" onclick = "validate()"/>
</p>
</body>
</html>The above is the detailed content of js implementation of random number and letter verification code example code. For more information, please follow other related articles on the PHP Chinese website!
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