[英]What is the value of ajax.responseText when there is no response being sent?
我写了一个JavaScript函数,用于检查用户名在数据库中是否可用。 如果用户名不可用,则ajax发送回文本响应,该响应会更改某些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,但是我只需要知道从ajax.responseText返回什么,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);
}
}
}
除非请求超时,否则总会有一个响应。 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。
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