简单的验证码

 var code; 
function createCode()
{ code = new Array();var codeLength = 4;
  var   checkCode = document.getElementById("checkCode"); 
   checkCode.value = "";
   var selectChar = new Array(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');
   for (var i = 0; i < codeLength; i++)

{ var charIndex = Math.floor(Math.random() * 32); code += selectChar[charIndex]; }

if (code.length != codeLength)

{ createCode(); }

checkCode.value = code;
 }