Xmlhttprequest Status 0 (Responsetext Is Empty)

XMLHttpRequest status 0 but responseText correct

Learn the basics

Before you START programming for Web you should understand what is HTTP, WebServer, Client, Protocol, Request, Response and Status Code.

Protocol file vs http

Protocol file:// don't work with XMLHttpRequest by browser security, prefer http://.
For use http:// in your PC/Machine install Apache or Nginx

You use PHP, .NET, Java (jsp or jsf) or something?

To start working with "WEB" is advisable to know a programming language and perhaps a framework:

• Django (Python FrameWork) install Django 1.6.2
• Django+Windows
• PHP+Windows install Wamp
• PHP+Linux (or Windows) install Xampp
• ASP.NET (asp.net is a framework, you can programing in C# or VB) install Microsoft ASP.NET
• JSF2 (Java is language and Facelets is "template"): http://balusc.blogspot.com.br/2011/01/jsf-20-tutorial-with-eclipse-and.html
• Rails (Ruby is language and Rails is "Framework"): http://rubyonrails.org/

Ajax vs Sjax

Ajax in Async-mode requires onreadystatechange

Ajax ("A"synchronous Javascript and XML):

var request = new XMLHttpRequest();
request.open("GET", "test.html", true);//true is "async"

request.onreadystatechange = function (event) {
    if (request.readyState==4) {
        console.log("status: "+request.status);
        console.log("response: "+request.responseText);
    }
};
request.send(null);

"SJAX" ("S"ynchronous Javascript and XML):

var request = new XMLHttpRequest();
request.open("GET", "test.html", false);//false is "sync"
request.send(null);
if (request.readyState==4) {
    console.log("status: "+request.status);
    console.log("response: "+request.responseText);
}

Prefer asynchronous mode, so that you can work multiple events without a need to wait for the other and also avoid freezing the "javascript".

XMLHttpRequest has a 200 status, but responseText is empty

You are using XMLHttpRequest in asynchronous mode:

xhr.open('POST', cloudinaryURL, true);

But your code is designed for synchronous mode:

xhr.open('POST', cloudinaryURL, false);

In asynchronous mode, xhr.send() will return immediately without actually processing the request. So, xhr.responseText hasn't been populated yet when you try to access it.

XMLHttpRequest responseText is empty

its not possible with ajax because of same origin policy , but to solve your problem you can use server side programming like PHP or Nodejs. basically PHP will be available in web hostings.

create getGoogle.php

 <?php 
    // create curl resource 
    $ch = curl_init(); 

    // set url 
    curl_setopt($ch, CURLOPT_URL, "www.google.de"); 

    //return the transfer as a string 
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 

    // $output contains the output string 
    $output = curl_exec($ch); 

    // close curl resource to free up system resources 
    curl_close($ch);  

    echo $output;    
  ?>

use your javascript as below

  <script type="text/javascript">

  var http = new XMLHttpRequest();

   http.open("GET", 'getGoogle.php', true);
   http.send(null);

   http.onreadystatechange = function() {
        alert(http.responseText);
   }

   alert("The end is reached");
   </script>

Hope this solves your problem. Cheers

xmlhttprequest status is always 0 and no response in responseText

This is a cross domain issue (CORS) which means you are trying to make a request (for a resource) from outside of your current domain. You need to allow set the Access-Control-Allow-Origin to accept all your requests.

You can do this by adding the below lines to your .js file (where you have your express.js code)

response.writeHead(200, {
    'Content-Type': 'text/plain',
    'Access-Control-Allow-Origin' : '*'
});

XMLHttpRequest status 4 but responseText is empty

alert(req_url) should show wrong url "http://www.domainname.comads/verifypublisher/"

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