Question

我编写了一个javascript函数，用于检查数据库中是否有用户名。如果用户名不可用，则ajax会发回文本响应，这会更改某些css并添加错误消息。当用户名可用时，ajax不会发送响应，这很好，但我只需要知道从ajax.responseText返回的是什么，因为没有值。我试过''和null。

function _(x) {
return document.getElementById(x);
}

function ajaxObj(meth, url) {
var x = new XMLHttpRequest(); 
x.open( meth, url, true );  
x.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); 
return x;
}
function ajaxReturn(x) {
if(x.readyState == 4 && x.status == 200) {
    return true;
    }
}
function verifyEmail(){

var email = _("email").value;
var status = _("estatus");     
var emailRegEx = /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i;


if (document.signupform.email.value.search(emailRegEx) == -1) {
    _("emaildiv").style.border = "1px solid #d33e3e";
    _("emaildiv").style.backgroundColor = "#fadede";
    status.innerHTML = "<br />Please enter a valid email address";
 } else {
    _("emaildiv").style.border = "";
    _("emaildiv").style.backgroundColor = "";
    status.innerHTML = "";

    if (email != "") {
        status.innerHTML = "checking. . . "; 
        var ajax = ajaxObj("POST", "fan_signup_local.php");    
        ajax.onreadystatechange = function() {
            if (ajaxReturn(ajax) == true) {
                status.innerHTML = ajax.responseText;
                console.log(status.innerHTML);
                if (status.innerHTML !== '') {
                    _("emaildiv").style.border = "1px solid #d33e3e";
                    _("emaildiv").style.backgroundColor = "#fadede";
                    console.log(ajax.responseText);
                } else {
                    _("emaildiv").style.border = "";
                    _("emaildiv").style.backgroundColor = "";
                }
            }
        }
        ajax.send("email="+email);
    }
 }
}

Answer 1

除非请求超时，否则总会有响应。如果服务器脚本退出而未打印任何内容，则响应将为空字符串。

没有响应发送时，ajax.responseText的值是多少？

1 个答案: