Develop Reference

In what order is XMLHttpRequest() executed

I am trying to figure out how to toggle the style display using plain javascript.
I have an XLMHttpRequest(). It works. The UI display is what I am working on. I would like the spin icon to show while the data is being loaded to the database. So, my code turns on the icon but the problem is when I add
document.getElementById('loading').style.display = "none";
to reset it to hidden. It never shows. So, here is my code.
function runScript()
{
let xhr = new XMLHttpRequest();
xhr.open('GET', 'wenoconnected.php', true);
xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xhr.onprogress = function() {
document.getElementById('loading').style.display = "block";
}
xhr.onreadystatechange = function () {
if(this.readyState == 4 && this.status == 200) {
console.log(this.responseText);
if (this.responseText === 'imported') {
alert('Update Complete');
}
document.getElementById('loading').style.display = "none";
}
}
xhr.send()
}
I tried to have the page just reload after the alert is shown but all that does is immediately reloads the page without executing the xhr.send(). That is why I would like to know what order is the code executed. That way I will know where to place the display = "none".

The latency is probably too low to notice the change (which can be verified by simulating high latency on the server). Try the following as an alternative:
From:
function runScript()
{
let xhr = new XMLHttpRequest();
xhr.open('GET', 'wenoconnected.php', true);
xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xhr.onprogress = function() {
document.getElementById('loading').style.display = "block";
}
xhr.onreadystatechange = function () {
if(this.readyState == 4 && this.status == 200) {
console.log(this.responseText);
if (this.responseText === 'imported') {
alert('Update Complete');
}
document.getElementById('loading').style.display = "none";
}
}
xhr.send()
}
To:
function runScript()
{
let xhr = new XMLHttpRequest();
xhr.open('GET', 'wenoconnected.php', true);
xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xhr.onreadystatechange = function () {
if(this.readyState == 4 && this.status == 200) {
console.log(this.responseText);
if (this.responseText === 'imported') {
alert('Update Complete');
}
document.getElementById('loading').style.display = "none";
}
}
document.getElementById('loading').style.display = "block";
xhr.send()
}
Assumptions:
The GET request latency is slow enough that you'll see the indicator
There is no other issue, related to CSS/HTML, that would prevent the indicator from showing
Disregarding the obvious, like; whether the function is being executed, no typos for identifiers that’d prevent relevant code from executing, etc.

javascript load new url in div?

I got this code, to simple to have any errors and still...
I have a nav, where the onclick calls for clicker(nodenr) what should load an external site in an div.
function clicker(nodenr) {
var url=links[nodenr];
console.log(nodenr);
var request = new XMLHttpRequest();
request.open('GET', ''+url+'', true);
//request.open('GET', ''url, true);
request.onreadystatechange = function (event) {
if(request.readyState == 4) {
if(request.status == 200) {
console.log("hello");
document.getElementById("content").innerHTML = request.responseText;
}
else {
document.getElementById("content").innerHTML = "Service not loading.";
}
}
};
}
What basic error have I made? Please correct me. :)

use 'XMLHttpRequest' to get external website's source - Javascript

is there any method to get external website's source with javascript and without use of jquery?
this code can't get external page source:
var request = new XMLHttpRequest();
request.open('GET', 'internal_page_only:(.html', true);
request.onload = function() {
if (request.status >= 200 && request.status < 400) {
// Success!
alert(request.responseText);
} else { //error }};
request.onerror = function() { //error };
request.send();

How to handle the err_blocked_by_client using Javascript?

My aim is to detect the ad-blocker. I found couple of good examples like FuckAdBlock.
When the ad service call is blocked by the ad-blocked we get the error "err_blocked_by_client".
I want to handle this error, in the following way :
var xhr = new XMLHttpRequest();
try
{
xhr.open("GET","http://static.adzerk.net/ados.js", false);
xhr.onreadystatechange = function (oEvent) {
if (xhr.readyState === 4) {
if (xhr.status === 200) {
console.log(xhr.responseText)
} else {
console.log("Error", xhr.statusText);
}
}
};
xhr.send();
}
catch(error)
{
console.log("ConsoleLog \n " + JSON.stringify(xhr));
console.log("Error Catched" + error);
}
But in this case i am not able to identify the error reason on catch block.
Please let me know the better option to handle this error or my mistake in this code.
Thanks

You need to have the xhr variable outside of your try. It fails on JSON.stringify(xhr) - because xhr is out of scope. You need to use the onerror error handler to handle the async XMLHttpRequest. You also need to remove the oEvent parameter from the function passed to onreadystatechange. See below:
var xhr = new XMLHttpRequest();
try
{
xhr.open("GET","http://static.adzerk.net/ados.js", true);
xhr.onreadystatechange = function () {
if (xhr.readyState === 4) {
if (xhr.status === 200) {
console.log(xhr.responseText)
} else {
console.log("Error", xhr.statusText);
}
}
};
xhr.onerror = function(e) {
console.log("Error Catched" + e.error);
};
xhr.send();
}
catch(error)
{
console.log("ConsoleLog \n " + JSON.stringify(xhr));
console.log("Error Catched" + error);
}

Ajax not working in firefox without alert

function processAjaxStateChangeForRowAdd() {
alert(0);
if (req.readyState == 4) { // Complete
if (req.status == 200) { // OK response
processForRowAdd(req.responseText);
} else {
alert("Problem: " + req.statusText);
}
}
}
This code is working fine for IE, Safari and Firefox, but if I remove the alert, then the code will not work in Firefox, though it still works in IE and Safari.
Can anybody give me suggestion why it not working in Firefox without alert?
EDIT: Code that adds a row:
if (window.XMLHttpRequest && browserVersion.indexOf("Microsoft") == -1 ) {
// code for Firefox, Chrome, Opera, Safari
req = new XMLHttpRequest("");
if (req) {
ajaxProcessed = false;
req.onreadystatechange = processAjaxStateChangeForRowAdd;
req.open("POST", url, true);
req.send();
// alert("1");
}
}

The alert is blocking. What this means is that your script is temporarily suspended (even if it's for a few milliseconds). During this time, your AJAX request completes and your req object is being set. You can add a delay (using setTimeout) to your callback to verify this.
I would suggest you post more of your script so that we can help you set up your callback properly. Alternatively, use a library such as jQuery to set up AJAX calls in a cross-browser manner easily.
EDIT: You need to either declare req as a global variable, or use an anonymous function. The following code demonstrates the first method (using a global variable):
var req;
if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
if (req) {
req.onreadystatechange = processAjaxStateChangeForRowAdd;
req.open("POST", url, true);
req.send();
}
}
function processAjaxStateChangeForRowAdd() {
if (req.readyState == 4) { // Complete
if (req.status == 200) { // OK response
processForRowAdd(req.responseText);
} else {
alert("Problem: " + req.statusText);
}
}
}

function getHttp()
{
var xmlhttp;
try
{
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
}
catch(e)
{
try
{
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
catch(e)
{
if(typeof XMLHttpRequest != 'undefiend')
{
xmlhttp = new XMLHttpRequest();
}
}
}
return xmlhttp;
}

can you try this:
if (request.readyState == 4) {
if (request.status == 200) {
var response = request.responseText;
} else
alert("status: " + request.status);
}

You should also check for the readyState , the following code might help
req.onreadystatechange=function()
{
if (req.readyState==4 && req.status==200)
{
processForRowAdd(req.responseText)
}
}
Read this for the different values of readyState