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XMLHttpRequest blocked in draw.io Electron app

I am desperatly trying to code a plugin for Draw.io that will basically do a request to another website in order to get some images.
It works fine on the local web version of Draw.io, but on the desktop version I get an empty responseText.
Here is what I'm simply doing in the plugin js:
Draw.loadPlugin(function(ui)
{
var data = null;
var xhr = new XMLHttpRequest();
xhr.open("GET", "https://jsonplaceholder.typicode.com/posts");
xhr.setRequestHeader("accept", "application/json");
xhr.send();
xhr.addEventListener("readystatechange", function () {
if (this.readyState === this.DONE) {
alert(this.responseText);
}
});
});
That is pretty basic and probably not working well but I should at least get an error... All I have is an empty response.
Does the Electron app blocks outside XHR? Is there a workaround? Thanks!

Not able to do post call using XMLHttpRequest

I am not able to make a post-call using xmlhttprequest in javascript. First, I am getting a 401 response code from server-side. Below is code I am using below code.
function makeRestCall(){
console.log("Rest call made")
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
alert(this.responseText);
}
};
xhttp.open("POST", "myurk", false, 'username', 'password');
xhttp.setRequestHeader("Content-type", "application/json");
xhttp.send()
alert(xhttp.status);
alert(xhttp.responseText)
I am also getting
"Request has been blocked by CORS policy"
I am able to do a rest call from postman and using basic auth and getting response also
I have referred various links for making a rest call using javascript.
Link 1 Link 2
But still, I am not able to resolve the error. Can anyone tell what is wrong am I doing.

Post to and visit a URL in Javascript

I'm trying to:
Post a JSON object to a URL and visit it at the same time.
Set the content-type and accept headers
I'm working with an old source base (asp classic / vb). Ideally, if I can do this in javascript it would be wonderful!
Constructing the js call with headers and data is simple with XHR:
var xhr = new XMLHttpRequest();
var url = "url";
xhr.open("POST", url, true);
xhr.setRequestHeader("Content-Type", "application/json");
var data = JSON.stringify({JSON DATA});
xhr.send(data);
However this is an async call and I can't seem to find a way of making it actually visit the URL in the browser.
The alternative is to create an form and append it to a HTML entity before using javascript to submit it. This time is post the data to and visits to the URL.. however, I don't have control over the headers.
So back to my questions. Can I post to and visit a URL in Javascript?

Given that visiting an URL in the browser is a GET request, and you want to POST at the same time, NO you cannot.
Why do you need to post and visit?
You could post your data and in the callback (once the post request is done) load the the page.

No.
The closest you could come would be to:
Use Ajax to make the request
Use DOM to modify the current page with data from the response
Use the History API to update the URL in the address bar
Changing the server side code to expect regular form encoded data and then submitting a regular form would probably be the simplest approach to solving the problem.

You are using XHR, and if you want to manage it from javascript... Add onreadystatechange property to your xhr (this function will be fired when your server response), and in this function redirect using window.location.href
var xhr = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
// Here redirect, with params if you need to
window.location.href = "https://stackoverflow.com?name1=value1&name2=value2";
}
};
var url = "url";
xhr.open("POST", url, true);
xhr.setRequestHeader("Content-Type", "application/json");
var data = JSON.stringify({JSON DATA});
xhr.send(data);

chrome extension http request to website

I wanted to make a chrome extension that gets the html code from this website: https://free-proxy-list.net/
without actually going to that webpage.
I tried using the steps here:
https://developer.chrome.com/extensions/xhr
but the request kept showing as undefined when I tried to print it out.
The script I was using was:
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == XMLHttpRequest.DONE) {
alert(xhr.responseText);
}
}
xhr.open('GET', "url", true);
xhr.send(null);
document.write(xhr.send());
Note: not putting url in code since SO won't let me post a question with more than 2 links.
How would I get the code from this website in a string variable that I can parse?

Safe Way to Send POST Request via Javascript

I'm currently sending POST requests to a PHP file of mine via a button with the following function:
function buttonFunction() {
$.post("http://ipaddress/core/file.php",{username:username, password:pword, coins:coins}, function(data) {
// Stuff
});
}
However, I recently found out that if the file process/PHP script is still running (trying to obtain the resulting data/response), and the user refreshes the page, the PHP process would still be running on the server. Also, if the user then decided to click the button again (after refreshing), there would be TWO PHP proccesses running from the same user on the server (that is, if the first one was still running):
Javascript Abort POST Request on Retry/Refresh (HIGH CPU Usage)
However, I came across sending POST data with XMLHttpRequest with Javascript:
Send POST data using XMLHttpRequest
So let's say I send my POST request this way, would it be safe to say when the user refreshes/closes out of the page, the PHP execution ends?
function buttonFunction() {
var http = new XMLHttpRequest();
var url = "get_data.php";
var params = "lorem=ipsum&name=binny";
http.open("POST", url, true);
//Send the proper header information along with the request
http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
http.setRequestHeader("Content-length", params.length);
http.setRequestHeader("Connection", "close");
http.onreadystatechange = function() {//Call a function when the state changes.
if(http.readyState == 4 && http.status == 200) {
alert(http.responseText);
}
}
http.send(params);
}
However, if this also does not work, how can I fix this issue (multiple scripts running in the background from the same user)? Whether that fix be in the PHP file or in the JavaScript itself, any help would be appreciated.
Edit 1:
Possible Solution?
What if I use XMLHttpRequest and abort the request before the page unloads?
window.onbeforeunload = function(event) {
http.abort();
};