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Eel application: download files in Browser

i´m currently using JavaScript and HTML with eel and Python. But unfortunately when I am trying to create a file in the Chrome-Browser window (as an download) over JS i can only download it once.
The second "download" is not working.
-> Chrome just shows this (as it does when it downloads something) but then nothing happens:
When I am using Edge browser or only JS without eel it works perfectly fine!
My JS function that creates the download: (string is a json string that is generated earlier).
var jsonLink = document.getElementById("jsonLink");
jsonLink.download = "exportedToJson.json";
jsonLink.href = "data:application/json;charset=utf-8," + encodeURIComponent(string);

Ok I found a solution:
My chrome browser was blocking more than one download from "localhost:8000". So I had to go to settings and allow more than one download.
Maybe this helps someone :)
Why did I not find this earlier:
When I started my Python script, it calls:
eel.start('index.html', mode='chrome', port=8000) #starting chrome
Which does open a new Chrome Tab without the Tabbar (so i did neither see the tabs nor my favorite sites). Therefore I did not get a notification when chrome stated that download is blocked.
But after starting the eel-local webserver and open localhost:8000 in my normal chrome window, I did get a notification and I was able to allow the downloads.
-> afterwards it also worked in this eel-chrome window.

How to Change Firefox Proxy Settings Programmatically?

I'm launching Firefox via command line and I'd like to launch a specific Firefox Profile with a proxy. According to this answer on Stackoverflow, Firefox proxy settings are stored in pref.js in the Firefox Profile folder and it is necessary to edit this file to launch FF with a proxy.
I've edited the file as follows:
user_pref("network.proxy.ftp", "1.0.0.1");
user_pref("network.proxy.ftp_port", 00000);
user_pref("network.proxy.gopher", "1.0.0.1");
user_pref("network.proxy.gopher_port", 00000);
user_pref("network.proxy.http", "1.0.0.1");
user_pref("network.proxy.http_port", 22222);
user_pref("network.proxy.no_proxies_on", "localhost, 1.0.0.1");
user_pref("network.proxy.socks", "1.0.0.1");
user_pref("network.proxy.socks_port", 00000);
user_pref("network.proxy.ssl", "1.0.0.1");
user_pref("network.proxy.ssl_port", 00000);
user_pref("network.proxy.type", 1);
Note: the IP address and port used above are for demonstration purposes.
However, I'm encountering two problems:
1) Firefox completely ignores these settings and launches FF without any proxy at all
2) When Firefox exits the text modification is reverted/deleted
Note: When I edited the text file above, Firefox was not running. I know there's a disclaimer at the top of prefs.js:
If you make changes to this file while the application is running, the
changes will be overwritten when the application exits.
But there were no live instances of Firefox running at the time I edited the above file.
Manually creating different FF Profiles (as suggested by another user) with different proxies is not an option as everything needs to be done programmatically, without manual intervention.
Does Firefox still support linking proxy via pref.js? If not, what is the current working solution to launch Firefox via command line with a proxy in Java?
Thanks

A proxy-autoconfig file is what you are looking for.
Docs here.
Define a file name.pac, that contains the javascript function
function FindProxyForURL(url, host)
Inside the file you can use any javscript you'd like to decide what proxy to use. Set the path to your .pac file in the firefox settings, under auto-config proxy. Remember to use a file url.
To setup automatic file switching, simply configure firefox to point towards a single file, and overwrite the file programmatically every time you want it to change. You could keep copies of all options, and simply copy an option file into the target file right before running.
An example of a super simple pac file is this:
function FindProxyForURL (url, host) {
return 'PROXY proxy.example.com:8080; DIRECT';
}
It will always return the identical proxy for all endpoints.
Passwords are not explicitly supported by the pac standard, but there are different ways to approach this. Firefox will prompt you for a login if it thinks it needs one, and you could also embed the password into the url (username:password#proxy.example.com). Additionally, a tool like proxy login automator could allow you to use passwords and to dynamically set the proxy without having to fight with firefox.

How to make a 'protocol' of my own and a Desktop application to use it for a Browser? [duplicate]

How do i set up a custom protocol handler in chrome? Something like:
myprotocol://testfile
I would need this to send a request to http://example.com?query=testfile, then send the httpresponse to my extension.

The following method registers an application to a URI Scheme. So, you can use mycustproto: in your HTML code to trigger a local application. It works on a Google Chrome Version 51.0.2704.79 m (64-bit).
I mainly used this method for printing document silently without the print dialog popping up. The result is pretty good and is a seamless solution to integrate the external application with the browser.
HTML code (simple):
Click Me
HTML code (alternative):
<input id="DealerName" />
<button id="PrintBtn"></button>
$('#PrintBtn').on('click', function(event){
event.preventDefault();
window.location.href = 'mycustproto:dealer ' + $('#DealerName').val();
});
URI Scheme will look like this:
You can create the URI Scheme manually in registry, or run the "mycustproto.reg" file (see below).
HKEY_CURRENT_USER\Software\Classes
mycustproto
(Default) = "URL:MyCustProto Protocol"
URL Protocol = ""
DefaultIcon
(Default) = "myprogram.exe,1"
shell
open
command
(Default) = "C:\Program Files\MyProgram\myprogram.exe" "%1"
mycustproto.reg example:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Classes\mycustproto]
"URL Protocol"="\"\""
#="\"URL:MyCustProto Protocol\""
[HKEY_CURRENT_USER\Software\Classes\mycustproto\DefaultIcon]
#="\"mycustproto.exe,1\""
[HKEY_CURRENT_USER\Software\Classes\mycustproto\shell]
[HKEY_CURRENT_USER\Software\Classes\mycustproto\shell\open]
[HKEY_CURRENT_USER\Software\Classes\mycustproto\shell\open\command]
#="\"C:\\Program Files\\MyProgram\\myprogram.exe\" \"%1\""
C# console application - myprogram.exe:
using System;
using System.Collections.Generic;
using System.Text;
namespace myprogram
{
class Program
{
static string ProcessInput(string s)
{
// TODO Verify and validate the input
// string as appropriate for your application.
return s;
}
static void Main(string[] args)
{
Console.WriteLine("Raw command-line: \n\t" + Environment.CommandLine);
Console.WriteLine("\n\nArguments:\n");
foreach (string s in args)
{
Console.WriteLine("\t" + ProcessInput(s));
}
Console.WriteLine("\nPress any key to continue...");
Console.ReadKey();
}
}
}
Try to run the program first to make sure the program has been placed in the correct path:
cmd> "C:\Program Files\MyProgram\myprogram.exe" "mycustproto:Hello World"
Click the link on your HTML page:
You will see a warning window popup for the first time.
To reset the external protocol handler setting in Chrome:
If you have ever accepted the custom protocol in Chrome and would like to reset the setting, do this (currently, there is no UI in Chrome to change the setting):
Edit "Local State" this file under this path:
C:\Users\Username\AppData\Local\Google\Chrome\User Data\
or Simply go to:
%USERPROFILE%\AppData\Local\Google\Chrome\User Data\
Then, search for this string: protocol_handler
You will see the custom protocol from there.
Note: Please close your Google Chrome before editing the file. Otherwise, the change you have made will be overwritten by Chrome.
Reference:
https://msdn.microsoft.com/en-us/library/aa767914(v=vs.85).aspx

Chrome 13 now supports the navigator.registerProtocolHandler API. For example,
navigator.registerProtocolHandler(
'web+custom', 'http://example.com/rph?q=%s', 'My App');
Note that your protocol name has to start with web+, with a few exceptions for common ones (like mailto, etc). For more details, see: http://updates.html5rocks.com/2011/06/Registering-a-custom-protocol-handler

This question is old now, but there's been a recent update to Chrome (at least where packaged apps are concerned)...
http://developer.chrome.com/apps/manifest/url_handlers
and
https://github.com/GoogleChrome/chrome-extensions-samples/blob/e716678b67fd30a5876a552b9665e9f847d6d84b/apps/samples/url-handler/README.md
It allows you to register a handler for a URL (as long as you own it). Sadly no myprotocol:// but at least you can do http://myprotocol.mysite.com and can create a webpage there that points people to the app in the app store.

This is how I did it. Your app would need to install a few reg keys on installation, then in any browser you can just link to foo:\anythingHere.txt and it will open your app and pass it that value.
This is not my code, just something I found on the web when searching the same question. Just change all "foo" in the text below to the protocol name you want and change the path to your exe as well.
(put this in to a text file as save as foo.reg on your desktop, then double click it to install the keys)
-----Below this line goes into the .reg file (NOT including this line)------
REGEDIT4
[HKEY_CLASSES_ROOT\foo]
#="URL:foo Protocol"
"URL Protocol"=""
[HKEY_CLASSES_ROOT\foo\shell]
[HKEY_CLASSES_ROOT\foo\shell\open]
[HKEY_CLASSES_ROOT\foo\shell\open\command]
#="\"C:\\Program Files (x86)\\Notepad++\\notepad++.exe\" \"%1\""

Not sure whether this is the right place for my answer, but as I found very few helpful threads and this was one of them, I am posting my solution here.
Problem: I wanted Linux Mint 19.2 Cinnamon to open Evolution when clicking on mailto links in Chromium. Gmail was registered as default handler in chrome://settings/handlers and I could not choose any other handler.
Solution:
Use the xdg-settings in the console
xdg-settings set default-url-scheme-handler mailto org.gnome.Evolution.desktop
Solution was found here https://alt.os.linux.ubuntu.narkive.com/U3Gy7inF/kubuntu-mailto-links-in-chrome-doesn-t-open-evolution and adapted for my case.

I've found the solution by Jun Hsieh and MuffinMan generally works when it comes to clicking links on pages in Chrome or pasting into the URL bar, but it doesn't seem to work in a specific case of passing the string on the command line.
For example, both of the following commands open a blank Chrome window which then does nothing.
"c:\Program Files (x86)\Google\Chrome\Application\chrome.exe" "foo://C:/test.txt"
"c:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --new-window "foo://C:/test.txt"
For comparison, feeding Chrome an http or https URL with either of these commands causes the web page to be opened.
This became apparent because one of our customers reported that clicking links for our product from a PDF being displayed within Adobe Reader fails to invoke our product when Chrome is the default browser. (It works fine with MSIE and Firefox as default, but not when either Chrome or Edge are default.)
I'm guessing that instead of just telling Windows to invoke the URL and letting Windows figure things out, the Adobe product is finding the default browser, which is Chrome in this case, and then passing the URL on the command line.
I'd be interested if anyone knows of Chrome security or other settings which might be relevant here so that Chrome will fully handle a protocol handler, even if it's provided via the command line. I've been looking but so far haven't found anything.
I've been testing this against Chrome 88.0.4324.182.

open
C:\Users\<Username>\AppData\Local\Google\Chrome\User Data\Default
open Preferences then search for excluded_schemes you will find it in 'protocol_handler' delete this excluded scheme(s) to reset chrome to open url with default application

Recover javascript logs and errors on Internet Explorer without F12 tool

The main idea is to run a random page on Internet Explorer and get javascript errors and logs.
Is there a way to recover javascript console logs and execution error
from a random web page without accessing the F12 tool on Internet
Explorer?
I found that with Chrome based browser, you can get it on your AppData file log by adding --enable-logging --v=1 args when launching.
Any solution with any language are welcome.
Thank you for your answer.
NOTE :
random page on Internet Explorer means that I do not have the access on the source code.

Basic solution to this would be:
1. Use Exception Handling to catch the errors.
2. Log errors in a Global Array
3. Log the errors in a file using Blob and URL.createObjectURL. All recent browsers support this.

Have you considered using a Bookmarklet that:
Overrides window.console.log and window.console.error (to intercept messages)
Logs incoming messages somewhere using createObjectURL?
Or you could use something like firebuglite and auto-enable it like this:
<script type="text/javascript" src="https://getfirebug.com/firebug-lite.js">
{
overrideConsole: false,
startInNewWindow: true,
startOpened: true,
enableTrace: true
}
</script>
More instructions are here: http://getfirebug.com/firebuglite

If the F12 tool is not of your interest, then what about the Event Viewer? Open Event Viewer from Control Panel -> System and Security -> Administrative Tools -> Event Viewer.‌ Then select the log Applications and Services Logs\Internet Explorer.
By default no events are being logged for Internet Explorer, to enable them create a new DWORD registry value named Feature_Enable_Compat_Logging under the following registry key:
HKCU\SOFTWARE\Microsoft\Windows\Internet Explorer\Main \FeatureControl
and set the registry value to 1.
Check the logs you get to see if it's what you're looking for.

One idea would be to write a browser extension which listens for window.onerror and writes to a file. Definitely not as elegant as the Chrome solution, but it would work fairly well.

Using local proxy might be a good one-time solution.
Charles web debugging proxy app has nice UI and it allows to replace any response with local resource.
So basically you'll need:
Download one any of the js files used on target page
add any code you wish to saved version
set up Charles to serve you your local version instead of remote one

You might try Fiddler. It's got its own logging and has amazing inspection power. It won't capture IE specific errors, since it's at a different layer, but it will definitely get you any code that's coming over the wire.

jQuery $.get from local directory producing different behaviour in IE vs FF, Chrome

I have the following simple jQuery:
$.get('Data.csv', function(data) {
alert(data);
});
Data.csv is stored in the same folder as the html file which accesses it.
If I run this in all browsers when the url is a domain (i.e. www.mysite.com/path/to/file), then the alert will display a string value of the contents of Data.csv.
If I create a hosts file link to the local folder (i.e. host.mysite.com/path/to/file) then alert will display a string value of the contents of Data.csv in all browsers.
If I run this in IE 9 when the url opens the file locally (i.e c:\path\to\file) then the alert will display a string value of the contents of Data.csv.
However, if I run this in FF or Chrome when the url opens the file locally (i.e file:///c:/path/to/file) then the alert will display [object XMLDocument].
Does anyone know why this is and how to open the local file as a string in FF and Chrome?
n.b. - I have tested this in order to rule out cross-platform-security issues. I don't think that that is the cause because otherwise it would not assign the content of the csv file at all.
Thanks in advance.

You're running into issues with the Same Origin Policy. If you look into your browser's console, you'll see something along the lines of Origin null is not allowed by Access-Control-Allow-Origin.
There's two possible fixes:
Run your stuff on a local web server like XAMPP, MAMP or the like.
Disable all web security on Chrome Startup, which you obviously don't want to do in real life. Wouldn't work in FF, either. So, stick with 1. ;)