使用XMLHttpRequest后返回false的问题 [英] Problems returning false after using XMLHttpRequest

问题描述

我发现了这个相关条目和其他一些条目，但我还没有找到答案，因此我正在发布新文章.我正在尝试使用对Ajax的了解从Javascript运行数据库查询.如果电子邮件已经在数据库中，我需要返回false，如果没有，则返回true，但是我似乎无法弄清楚自己在做什么错.在开始弄乱和弄乱之前，我已经发布了我的第一次尝试.

I have found this Related entry and a few others but I have not quite found my answer so I am posting new. I am trying to run a database query from Javascript using what I understand of Ajax. I need to return false if the email is already in the database and return true if it does not, but I cannot seem to figure out what I am doing wrong. I have posted my first attempt before I started messing around and making it messy.

javascript:无论如何，它似乎都返回true.

javascript: It seems to return true no matter what.

function emailvalid(){

var email = document.getElementById('email').value;
var confirmemail = document.getElementById('cemail').value;
if(email != '' && confirmemail != '')
{
    if(email == '')
    {
        document.getElementById('email').style.backgroundColor ='red';
        document.getElementById('tdemail').style.color = 'red';
        document.getElementById('tdemail').innerHTML = 'You must enter a valid email address.';
        document.getElementById('tdcemail').innerHTML = '';
        document.getElementById('cemail').value = '';
        return false;
    }

xmlhttp = new XMLHttpRequest();
var url="phpfiles/checkemail.php";
url = url+"?email="+email+"&cemail="+confirmemail;
xmlhttp.onreadystatechange = function()
{
    if (xmlhttp.readyState==4)
    {
        var answer = xmlhttp.responseText;
        if(answer == 'r0')
        {

        document.getElementById('email').style.backgroundColor ='green';
        document.getElementById('tdemail').style.color = 'red';
        document.getElementById('tdemail').innerHTML = 'This email address is already associated with an exiting account. Please login or use a different email address.';
        document.getElementById('tdcemail').innerHTML = '';
        document.getElementById('cemail').value = '';
        return false;
        }
        else if(answer == 'r1')
        {

        document.getElementById('tdemail').style.color = 'green';
        document.getElementById('email').style.backgroundColor ='green';
        document.getElementById('tdemail').innerHTML = "Emails match and are valid";
        document.getElementById('tdcemail').style.color = 'green';
        document.getElementById('tdcemail').innerHTML = "Emails match and are valid";
        document.getElementById('cemail').style.backgroundColor ='green';
        return true;
        }
        else if(answer == 'r2')
        {

        document.getElementById('tdemail').style.color = 'red';
        document.getElementById('email').style.backgroundColor ='red';
        document.getElementById('tdemail').innerHTML = "Email is not valid";
        document.getElementById('tdcemail').style.color = 'red';
        document.getElementById('tdcemail').innerHTML = "Email is not valid.";
        document.getElementById('cemail').style.backgroundColor ='red';
        return false;
        }
        else if(answer == 'r3')
        {

        document.getElementById('tdemail').style.color = 'green';
        document.getElementById('email').style.backgroundColor ='green';
        document.getElementById('tdemail').innerHTML = "Email is valid";
        document.getElementById('tdcemail').style.color = 'red';
        document.getElementById('tdcemail').innerHTML = "Emails do not match";
        document.getElementById('cemail').style.backgroundColor ='red';
        return false;
        }
        else if(answer == 'r4')
        {

        document.getElementById('tdemail').style.color = 'red';
        document.getElementById('email').style.backgroundColor ='red';
        document.getElementById('tdemail').innerHTML = 'Please enter a valid email address.';
        document.getElementById('tdcemail').style.color = 'red';
        document.getElementById('tdcemail').innerHTML = 'Please enter a valid email address.';
        document.getElementById('cemail').style.backgroundColor ='red';
        return false;
        }
    }
}
    xmlhttp.open("GET",url,true);
    xmlhttp.send(null);

}
else
{
    document.getElementById('tdemail').style.color = 'red';
    document.getElementById('email').style.backgroundColor ='red';
    document.getElementById('tdemail').innerHTML = "Email is not valid";
    document.getElementById('tdcemail').style.color = 'red';
    document.getElementById('tdcemail').innerHTML = "Email is not valid.";
    document.getElementById('cemail').style.backgroundColor ='red';
    return false;
}
}

innerHTML东西工作正常，这也是为什么我感到困惑的原因.

The innerHTML stuff works just fine which is also why I am confused.

php:据我所知，工作正常.

php: works fine as far as I can tell.

<?php
$email = $_GET['email'];
$cemail = $_GET['cemail'];
$emailvalidstring = "/^[a-z0-9]+([_\\.-][a-z0-9]+)*@([a-z0-9]+([\.-][a-z0-9]+)*)+\\.[a-z]{2,}$/i";
include('connection.php');

$checkemailquery = "SELECT email FROM users WHERE email='".$email."'";
$checkemailresult = mysql_query($checkemailquery);

// if query failed.
if(!$checkemailresult)
{
    $error = mysql_error();
    print $error;
    exit;
}
//if the query did run, the email exists. Print error and exit.
if(mysql_affected_rows() != 0)
{
    echo "r0";
    return false;   
}
else{
    if(preg_match($emailvalidstring, $email) && $email == $cemail)
    {
        echo "r1";
        return true;
    }
    else if(!preg_match($emailvalidstring, $email) && $email == $cemail)
    {
            echo "r2";
            return false;
    }
    else if(preg_match($emailvalidstring, $email) && $email != $cemail)
    { 
        echo "r3";
        return false;
    }
    else if(!preg_match($emailvalidstring, $email) && $email != $cemail)
    {
        echo "r4";
        return false;   
    }
}
?>

html:我先进行了两次检查，一次是警告用户是否已被使用，然后在服务器上进行第二次检查以确保它仍然是正确的. cemail是确认电子邮件.

html: I have it do a double check, once to alert the user if it is already taken, and then a second check on the server to make sure it is still true. cemail is the confirmation email.

<form  id="newaccount" name="newaccount" method="post" action="phpfiles/accountcode.php" onSubmit="return emailvalid()" >
<input type="text" id="email" onBlur="emailvalid()"/>
<input type="text" id="cemail" onBlur="emailvalid()" />
<input type="submit" value="New"/>
</form>

谢谢大家的帮助.我希望我已经安排好了.我对任何想法都持开放态度，因为我对此很陌生.

Thank you all for your help. I hope I have laid it out well enough. I am open to ANY ideas as I am rather new at this.

推荐答案

您将在匿名回调函数中返回false，而不是在emailValid函数中返回.只需声明一个全局布尔变量，然后在匿名回调函数中进行相应的更改即可.

You're returning false in the anonymous callback function not in the emailValid function. Just declare a global boolean variable and alter it accordingly in the anonymous callback function.

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