javascript - 提交前检查电子邮件无效

Question

如何检查电子邮件是否已被占用？我找到了一个脚本，但它仅显示“正在检查..”，如果电子邮件存在，我无法获得确切的结果。下面有代码:

<span id="usernamestatus"></span> 
<input type="text" onblur="checkusername()" id="sign_up_email_input_first" name="email_sign_up" placeholder="E-Mail">

        function checkusername() {
                var status = document.getElementById("usernamestatus");
                var u = document.getElementById("sign_up_email_input_first").value;
                if ( u !="") {
                    status.innerHTML = 'checking...';
                    var hr = new XMLHttpRequest();
                    hr.open("POST", "name_check.php", true);
                    hr.setRequestHeader("Content-type", "application/x-www-form-urlendcoded");
                    hr.onreadystatechange = function(){
                        if (hr.readyState == 4 && hr.status ==200) {
                            status.innerHTML = hr.responseText;
                        }
                    }
                    var v = "name2check="+u;
                    hr.send(v);
                }
            }

name_check.php

    if(isset($_POST['sign_up_email_input_first']) && $_POST['sign_up_email_input_first'] != "") {
        $username = $_POST['sign_up_email_input_first'];
        $sql_name_check = mysql_query("SELECT id FROM users WHERE email = '$username' LIMIT 1");
        $uname_check= mysql_num_rows($sql_name_check);
        if(strlen($username)<4){
            echo "You have invalid e mial adress";
            exit();
        }
        if($uname_check <1){
            echo "<strong>". $username. "</strong> Is OK";
            exit();
        }else{
            echo "<strong>" .$username. "</strong> is taken!";
            exit();
        }
    }                                                        

Answer 1

在您的 PHP 文件中，替换

$_POST['sign_up_email_input_first']

与:

$_POST['email_sign_up']

您基本上是通过名称而不是 ID 来获取值