Develop Reference

Cannot retrieve text from xampp server because XMLHttprequest.readystate always returns 'undefined'

I tried to access a .txt file stored in the htdocs folder of my xampp installation using only Javascript and no PHP. I only intend to use ajax to process a text file stored in server. This is my javascript code to make an asynchronous request:
(function(global){
var ajaxUtils = {};
function getRequestObject(){
if(window.XMLHttpRequest){
return (new XMLHttpRequest());
}
else{
global.alert('Ajax is not supported!');
return(null);
}
}
ajaxUtils.sendGetRequest = function(requestUrl, responseHandler){
var request = getRequestObject();
request.onreadystatechange = function(){
handleResponse(request, responseHandler);
};
request.open("GET",requestUrl,true);
request.send(null);
}
function handleResponse(request, responseHandler){
console.log(request.readystate + " " + request.status);
if((request.readystate == 4) && (request.status == 200)){
responseHandler(request);
}
}
global.$ajaxUtils = ajaxUtils;
})(window);
This is how I passed parameters to ajaxUtils.sendGetRequest():
document.addEventListener("DOMContentLoaded", function(event){
document.querySelector("button").addEventListener('click', function(){
this.textContent='Said it!';
$ajaxUtils.sendGetRequest('http://localhost/ajax/file.txt',function(request){
var name = request.responseText;
var message = "<h2>Hello " + name + '!</h2>';
document.getElementById('content').innerHTML=message;
});
});
});
The code didn't work and this is what I got in the console: request.readystate always returns 'undefined'
'readystate' property of XMLHttprequest can have values 0,1,2,3, or 4, but here it always returns 'undefined'. Does anybody know why this happened?

I can't get a response from the server

I followed some guides on how to send json objects to the server(written using node.js) and it doesn't work, I have no idea what is wrong. I know that my server works fine since I tested it on postman so it's my js code that's the problem, all the tutorials I see follow a similar XMLHttpRequest format.
this is my code
var ing = new Ingredient(name, date, qty, rp);
var url = "http://localhost:8081/addIngredient";
var xhr = new XMLHttpRequest();
xhr.open("POST", url, true);
//Send the proper header information along with the request
// application/json is sending json format data
xhr.setRequestHeader("Content-type", "application/json");
// Create a state change callback
xhr.onreadystatechange = function () {
if (xhr.readyState === 4 && xhr.status === 200) {
// Print received data from server
result.innerHTML = this.responseText;
}
};
// Converting JSON data to string
var data = JSON.stringify(ing);
document.write(data);
// Sending data with the request
xhr.send(data);
I used document.write to check where the code stops working but everything passes (since the document.write prints something), I suspect that there is something wrong/missing from xhr.send(data) but I can't tell what. Finally, nothing gets printed from the callback.

It's better to use onload instead of onreadystatechange
xhr.onload = function() {
if (xhr.status == 200) {
console.log(`Response length = ${xhr.response.length}`);
// store xhr.response here somewhere
}
};

How do i correctly format parameters passed server-side using javascript?

I cannot figure out how to get the following code working in my little demo ASP.NET application, and am hoping someone here can help.
Here is the javascript:
function checkUserName() {
var request = createRequest();
if (request == null) {
alert("Unable to create request.");
} else {
var theName = document.getElementById("username").value;
var userName = escape(theName);
var url = "Default.aspx/CheckName";
request.onreadystatechange = createStateChangeCallback(request);
request.open("GET", url, true);
request.setRequestHeader("Content-Type", "application/json");
//none of my attempts to set the 'values' parameter work
var values = //JSON.stringify({userName:"userName"}); //"{userName:'temp name'}"; //JSON.stringify({ "userName":userName });
request.send(values);
}
}
Here is the method in my *.aspx.cs class:
[WebMethod]
[ScriptMethod(UseHttpGet=true)]
public static string CheckName(string userName)
{
string s = "userName";
return s + " modified backstage";
}
When this code runs I receive this exception:
---------------------------
Message from webpage
---------------------------
{"Message":"Invalid web service call, missing value for parameter: \u0027userName\u0027.","StackTrace":" at System.Web.Script.Services.WebServiceMethodData.CallMethod(Object target, IDictionary`2 parameters)\r\n at System.Web.Script.Services.WebServiceMethodData.CallMethodFromRawParams(Object target, IDictionary`2 parameters)\r\n at System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams)\r\n at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.InvalidOperationException"}
---------------------------
OK
---------------------------
I started searching here, then went on to several threads on SO, trying quite a few combinations of quotation marks and key-value pairs, but nothing I've tried has worked.
When I remove the parameter from the C# method and request.send(), I get a response in my JS callback that I can work with. But as soon as I try to do something with parameters, I get the above exception. I'd like to know how to do this without using jQuery, if possible.
Thanks in advance.
FINAL VERSION
Using Alexei's advice, I ended up with the following, which works. The URL was missing the apostrophes on either end of the parameter value; this was keeping the call from going through.
function checkUserName() {
var request = createRequest();
if (request == null) {
alert("Unable to create request.");
} else {
var theName = document.getElementById("username").value;
var userName = encodeURIComponent(theName);
var url = "Default.aspx/CheckName?name='" + theName + "'";
request.onreadystatechange = createStateChangeCallback(request);
request.open("GET", url, true);
request.setRequestHeader("Content-Type", "application/json");
request.send();
}
}

request.send(values);
This won't work with a "GET". Try
request.open("POST", url, true);
http://www.w3schools.com/ajax/ajax_xmlhttprequest_send.asp

You need to:
decide whether you want GET or POST. For GET request you need all parameters to be in Url (and body to be empty), for POST you can use both. As of current code you are expecting GET, but sending POST.
properly add query parameter - name and encoded value. encodeUriComponent is JavaScript function of choice, see Build URL from Form Fields with Javascript or jquery for details
if using POST you need to properly encode parameters there too as well specify correct "content-type" header.
if sending JSON you need to decode JSON server side.
Alternatively you can use hidden form to perform POST/GET as covered in JavaScript post request like a form submit
Side note: jQuery.ajax does most of that for you and good source to look through if you want to do all yourself.

Like Alan said, use the POST method. Or pass your arguments in your URL before opening it, e.g.
var url = "Default.aspx/CheckName?userName=" + values;
EDIT : no, it's probably a bad idea since you want to send JSON, forget what I said.

If you need to go for POST, then you need to send it like this.
var values = JSON.stringify({"'userName':'"+ userName+ "'"});
And you have to change HttpGet to HttpPost

Given that your server side method asks for GET, you need:
request.open("GET", url + "?username=" + userName, true);
request.send();
The works for me:
function checkUserName() {
var request = new XMLHttpRequest();
if (request == null) {
alert("Unable to create request.");
} else {
var userName = "Shaun Luttin";
var url = '#Url.RouteUrl(new{ action="CheckName", controller="Home"})';
request.onreadystatechange = function() {
if (request.readyState == XMLHttpRequest.DONE ) {
if(request.status == 200){
document.getElementById("myDiv").innerHTML = request.responseText;
}
else if(request.status == 400) {
alert('There was an error 400')
}
else {
alert('something else other than 200 was returned')
}
}
}
request.open("GET", url + "?username=" + userName, true);
request.send();
}
}
With this on the server side:
[HttpGet]
public string CheckName(string userName)
{
return userName + " modified backstage";
}

XMLHttpRequest sometimes doesn't send string

I'm not sure why this is happening but I will try to explain as much as I already know.
I have a website that allows you to log in with an account stored on a database. Each user can update their own set of data that is also in the same database.
When a user changes data Javascript will post an XMLHttpRequest to a php file on the server. The data is JSON encoded and is decoded in the php file and then stores the data on the database.
The problem is whenever I log into a specific account no data is sent. The string is empty after the request is sent. The post works and the php file runs but no data is present. Here is my code for sending the request in JS:
function sendXMLHttpRequest(data, phpfile){
var xhr;
if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
}
else if (window.ActiveXObject) {
xhr = new ActiveXObject("Msxml2.XMLHTTP");
}
else {
throw new Error("Ajax is not supported by this browser");
}
xhr.open('POST', phpfile, true);
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.onreadystatechange = function () {
if (xhr.readyState === 4) {
if (xhr.status === 200) {
if (this.responseText !== null)
document.getElementById('saveresponse').innerHTML = xhr.responseText;
else
alert("Ajax error: No data received");
}else alert("Ajax error: " + this.status);
}
};
xhr.send(data);
}
On the php side:
session_start();
$mysql = new Mysql();
$data = json_decode($_POST['stringData']);
echo 'Data: ' . $data . "<br />";
Normally when I echo the data is returns Array which is what I want but it doesn't echo anything when ever I log into this one specific account, the data sent is just a string where stringData is a JSON. Is there a way to see if anything IS stored there? Also if nothing is being sent why could this be? Any suggestions for my code?

Make sure the request doesn't get cached by adding a random parameter:
querystring = 'validate=' + validate+ "&rand=" + new Date().getTime();

Form submit using Ajax

I need to submit the a form using Ajax with POST method.The code is as follows,
function persistPage(divID,url,method){
var scriptId = "inlineScript_" + divID;
var xmlRequest = getXMLHttpRequest();
xmlRequest.open("POST",url,true);
xmlRequest.onreadystatechange = function(){
alert(xmlRequest.readyState + " :" + xmlRequest.status);
if (xmlRequest.readyState ==4 || xmlRequest.status == 200)
document.getElementById(divID).innerHTML=xmlRequest.responseText;
};
xmlRequest.open("POST", url, false);
alert(xmlRequest.readyState);
xmlRequest.send(null);
}
but the form is not submitting(request is not executed or no data posted).How to submit the form using Ajax.
Thanks

There's a few reasons why your code doesn't work. Allow me to break it down and go over the issues one by one. I'll start of with the last (but biggest) problem:
xmlRequest.send(null);
My guess is, you've based your code on a GET example, where the send method is called with null, or even undefined as a parameter (xhr.send()). This is because the url contains the data in a GET request (.php?param1=val1&param2=val2...). When using post, you're going to have to pass the data to the send method.
But Let's not get ahead of ourselves:
function persistPage(divID,url,method)
{
var scriptId = "inlineScript_" + divID;
var xmlRequest = getXMLHttpRequest();//be advised, older IE's don't support this
xmlRequest.open("POST",url,true);
//Set additional headers:
xmlRequest.setRequestHeader('X-Requested-With', 'XMLHttpRequest');//marks ajax request
xmlRequest.setRequestHeader('Content-type', 'application/x-www-form-urlencode');//sending form
The first of the two headers is not always a necessity, but it's better to be safe than sorry, IMO. Now, onward:
xmlRequest.onreadystatechange = function()
{
alert(xmlRequest.readyState + " :" + xmlRequest.status);
if (xmlRequest.readyState ==4 || xmlRequest.status == 200)
document.getElementById(divID).innerHTML=xmlRequest.responseText;
};
This code has a number of issues. You're assigning a method to an object, so there's no need to refer to your object using xmlRequest, though technically valid here, this will break once you move the callback function outside the persistPage function. The xmlRequest variable is local to the function's scope, and cannot be accessed outside it. Besides, as I said before, it's a method: this points to the object directlyYour if statement is a bit weird, too: the readystate must be 4, and status == 200, not or. So:
xmlRequest.onreadystatechange = function()
{
alert(this.readyState + " :" + this.status);
if (this.readyState === 4 && this.status === 200)
{
document.getElementById(divID).innerHTML=this.responseText;
}
};
xmlRequest.open("POST", url, false);
alert(xmlRequest.readyState);//pointless --> ajax is async, so it will alert 0, I think
xmlRequest.send(data);//<-- data goes here
}
How you fill the data is up to you, but make sure the format matches the header: in this case 'content type','x-www-form-urlencode'. Here's a full example of just such a request, it's not exactly a world beater, since I was in the process of ditching jQ in favour of pure JS at the time, but it's serviceable and you might pick up a thing or two. Especially take a closer look at function ajax() definition. In it you'll see a X-browser way to create an xhr-object, and there's a function in there to stringify forms, too
POINTLESS UPDATE:
Just for completeness sake, I'll add a full example:
function getXhr()
{
try
{
return XMLHttpRequest();
}
catch (error)
{
try
{
return new ActiveXObject('Msxml2.XMLHTTP');
}
catch(error)
{
try
{
return new ActiveXObject('Microsoft.XMLHTTP');
}
catch(error)
{
//throw new Error('no Ajax support?');
alert('You have a hopelessly outdated browser');
location.href = 'http://www.mozilla.org/en-US/firefox/';
}
}
}
}
function formalizeObject(form)
{//we'll use this to create our send-data
recursion = recursion || false;
if (typeof form !== 'object')
{
throw new Error('no object provided');
}
var ret = '';
form = form.elements || form;//double check for elements node-list
for (var i=0;i<form.length;i++)
{
if (form[i].type === 'checkbox' || form[i].type === 'radio')
{
if (form[i].checked)
{
ret += (ret.length ? '&' : '') + form[i].name + '=' + form[i].value;
}
continue;
}
ret += (ret.length ? '&' : '') + form[i].name +'='+ form[i].value;
}
return encodeURI(ret);
}
function persistPage(divID,url,method)
{
var scriptId = "inlineScript_" + divID;
var xmlRequest = getXhr();
xmlRequest.open("POST",url,true);
xmlRequest.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
xmlRequest.setRequestHeader('Content-type', 'application/x-www-form-urlencode');
xmlRequest.onreadystatechange = function()
{
alert(this.readyState + " :" + this.status);
if (this.readyState === 4 && this.status === 200)
{
document.getElementById(divID).innerHTML=this.responseText;
}
};
xmlRequest.open("POST", url, false);
alert(xmlRequest.readyState);
xmlRequest.send(formalizeObject(document.getElementById('formId').elements));
}
Just for fun: this code, untested, but should work allright. Though, on each request the persistPage will create a new function object and assign it to the onreadystate event of xmlRequest. You could write this code so that you'll only need to create 1 function. I'm not going into my beloved closures right now (I think you have enough on your plate with this), but it's important to know that functions are objects, and have properties, just like everything else:Replace:
xmlRequest.onreadystatechange = function()
{
alert(this.readyState + " :" + this.status);
if (this.readyState === 4 && this.status === 200)
{
document.getElementById(divID).innerHTML=this.responseText;
}
};
With this:
//inside persistPage function:
xmlRequest.onreadystatechange = formSubmitSuccess;
formSubmitSuccess.divID = divID;//<== assign property to function
//global scope
function formSubmitSuccess()
{
if (this.readyState === 4 && this.status === 200)
{
console.log(this.responseText);
document.getElementById(formSubmitSuccess.divID).innerHTML = this.responseText;
//^^ uses property, set in persistPAge function
}
}
Don't use this though, as async calls could still be running while you're reassigning the property, causing mayhem. If the id is always going to be the same, you can, though (but closures would be even better, then).
Ok, I'll leave it at that

This code can let you understand. The function SendRequest send the request and build the xmlRequest through the GetXMLHttpRequest function
function SendRequest() {
var xmlRequest = GetXMLHttpRequest(),
if(xmlRequest) {
xmlRequest.open("POST", '/urlToPost', true)
xmlRequest.setRequestHeader("connection", "close");
xmlRequest.onreadystatechange = function() {
if (xmlRequest.status == 200) {
// Success
}
else {
// Some errors occured
}
};
xmlRequest.send(null);
}
}
function GetXMLHttpRequest() {
if (navigator.userAgent.indexOf("MSIE") != (-1)) {
var theClass = "Msxml2.XMLHTTP";
if (navigator.appVersion.indexOf("MSIE 5.5") != (-1)) {
theClass = "Microsoft.XMLHTTP";
}
try {
objectXMLHTTP = new ActivexObject(theClass);
return objectXMLHTTP;
}
catch (e) {
alert("Errore: the Activex will not be executed!");
}
}
else if (navigator.userAgent.indexOf("Mozilla") != (-1)) {
objectXMLHTTP = new XMLHttpRequest();
return objectXMLHTTP;
}
else {
alert("!Browser not supported!");
}
}

take a look at this page. In this line: req.send(postData); post data is an array with values that should be posted to server. You have null there. so nothing is posted. You just call request and send no data. In your case you must collect all values from your form, as XMLHTTPRequest is not something that can simply submit form. You must pass all values with JS:
var postData = {};
postData.value1 = document.getElementById("value1id").value;
...
xmlRequest.send(postData);
Where value1 will be available on server like $_POST['value'] (in PHP)
Also there might be a problem with URL or how you are calling persistPage. persistPage code looks ok to me, but maybe I'm missing something. Also you can take a look if you have no errors in console. Press F12 in any browser and find console tab. In FF you may need to install Firebug extention. Also there you will have Network tab with all requests. Open Firebug/Web Inspector(Chrome)/Developer Toolbar(IE) and check if new request is registered in its network tab after you call persistPage.

I found you've invoked the
xmlRequest.open()
method twice, one with async param as true and the other as false. What exactly do you intend to do?
xmlRequest.open("POST", url, true);
...
xmlRequest.open("POST", url, false);
If you want to send asynchronous request, pls pass the param as true.
And also, to use 'POST' method, you'd better send the request header as suggested by Elias,
xmlRequest.setRequestHeader('Content-type', 'application/x-www-form-urlencode');
Otherwise, you may still get unexpected issues.
If you want a synchronous request, actually you may handle the response directly right after you send the request, just like:
xmlRequest.open("POST", url, false);
xmlRequest.send(postData);
// handle response here
document.getElementById(scriptId).innerHTML = xmlRequest.responseText;
Hope this helps.