废话不多说，实现js登录验证码的功能需要下面两步，具体实现过程如下所示：
1.js
var code="" ; //在全局 定义验证码
function createCode(){
code = "";
var codeLength = 6;//验证码的长度
var checkCode = document.getElementById("checkCode");
checkCode.value = "";
var selectChar = new Array(0,1,2,3,4,5,6,7,8,9,'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();
}
document.getElementById("checkCode").innerHTML = code;
}
function validate () {
var inputCode = document.getElementById("checkNum").value.toUpperCase();
if(inputCode.length <=0) {
alert("请输入验证码！");
return false;
}
else if(inputCode != code ){
alert("验证码输入错误！");
createCode();
return false;
}
else {
alert("验证码通过！");
return true;
}
}
2.html
<body onload="createCode();"> <input type="text" value="" id="checkNum" /> <a id="checkCode" onclick="createCode()"></a> <input type="button" class="btnCheck" id="gotoCheck" value="验证" onclick="validate();" />
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