JS 实现随机验证码功能

 <div>   <input type = "text" id = "input" value="" />   <input type = "button" id="code" onclick="createCode()"/>   <input type = "button" value = "验证" onclick = "validate()"/>  </div> 

 #code{     font-family:Arial;     font-style:italic;     font-weight:bold;     border:0;     letter-spacing:2px;     color:blue;    }

//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{   window.open('http://www.baidu.com','_self');  } } //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(); }