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

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

//設置一個全局的變量，便于保存驗證碼 var code; function createCode(){  //首先默認code為空字符串  code = '';  //設置長度，這里看需求，我這里設置了4  var codeLength = 4;  var codeV = document.getElementById('code');  //設置隨機字符  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');  //循環codeLength 我設置的4就是循環4次  for(var i = 0; i < codeLength; i++){   //設置隨機數范圍,這設置為0 ~ 36    var index = Math.floor(Math.random()*36);    //字符串拼接 將每次隨機的字符 進行拼接    code += random[index];   }  //將拼接好的字符串賦值給展示的Value  codeV.value = code; } //下面就是判斷是否== 的代碼，無需解釋 function validate(){  var oValue = document.getElementById('input').value.toUpperCase();  if(oValue ==0){   alert('請輸入驗證碼');  }else if(oValue != code){   alert('驗證碼不正確，請重新輸入');   oValue = ' ';   createCode();  }else{   window.open('http://www.baidu.com','_self');  } } //設置此處的原因是每次進入界面展示一個隨機的驗證碼，不設置則為空 window.onload = function (){  createCode(); }