ajax防止表单自动提交

重写表单的checkForm方法，并用if和else解决异步判断的问题。

function checkForm(){
 1 var flag = false;    

$.ajaxSetup({async : false});

$.post(<?php echo "'".$SITE_PHP.'captchaAjax.php'."'";?>,'captcha='+document.getElementById("captcha").value,function(msg){if(!parseInt(msg)){layer.alert('验证码错误！',{time:1000});return flag;}else{

$.post(<?php echo "'".$SITE_PHP.'loginNamePassAjax.php'."'";?>,'username='+document.getElementById("username").value+'&'+'password='+document.getElementById("password").value,function(msg){if(!parseInt(msg)){layer.alert('用户名或密码错误！',{time:1000});return flag;}else{

flag = true;return flag;}});}});

return flag;
}