js验证密码必须为大小写字母和数字组成

<script language="JavaScript" type="text/JavaScript">
function checkPass(pass){
if(pass.length < 6){  
    return 0;  
}
var ls = 0;
if(pass.match(/([a-z])+/)){  
    ls++;  
}  
if(pass.match(/([0-9])+/)){  
    ls++;    
}  
if(pass.match(/([A-Z])+/)){  
    ls++;  
}  
if(pass.match(/[^a-zA-Z0-9]+/)){
    ls++;  
}  
    return ls;
}  
function Validate(){
var oldLogPWD = document.InfoForm.oldLogPWD;
var newLogPWD = document.InfoForm.newLogPWD;
var confirmLogPWD = document.InfoForm.confirmLogPWD;

if(oldLogPWD.value.checkEmpty()){
alert("旧登录密码不能为空!")
oldLogPWD.focus();
return false;
}
if(newLogPWD.value.checkEmpty()){
alert("新登录密码不能为空!")
newLogPWD.focus();
return false;
}
if(checkPass(newLogPWD.value)<3){
alert("新登录密码复杂度不够，请重新设置！");  
newLogPWD.focus();  
return false ;  
}
if(newLogPWD.value!=confirmLogPWD.value){
alert("确认新登录密码必须和新登录密码相等!");
confirmLogPWD.focus();
return false;
}
if(newLogPWD.value==oldLogPWD.value){
    alert("新登录密码不可以与旧登录密码相等!");
newLogPWD.focus();
return false;
}
return true;
}
function SubmitForm(){
if(Validate()){
var con;
   con=confirm("请牢记您的密码,确认执行该操作吗？");
   if(con==true){
  document.InfoForm.submit();
  }
  }
}
</script>