js生成验证码

function validateCode (codediv,codeinput){
this.codediv = codediv;
this.codeinput = codeinput;
this.create = function () {
window.code = "";
var codeLength = 6;
var checkCode = document.getElementById(this.codediv);
var selectChar = 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');

for (var i = 0; i < codeLength; i++) {
var charIndex = Math.floor(Math.random() * 36);
code += selectChar[charIndex];
}
//alert(code);
if (checkCode) {
checkCode.value = code;
}
}

this.validate = function(){
var inputCode = document.getElementById(this.codeinput).value;
if (inputCode.length <= 0) {
alert("请输入验证码！");
} else if (inputCode != code) {
alert("验证码错误！");
this.create();
} else {
//

}
}
}