Why doesn't socket.io work on iOS and Firefox?

Question

Angular

Good afternoon.
I use feathers/client + socket.io-client and when connecting to the front I use this code:

this._socket = io(environment.domain.api, {
      transports: ['websocket']
});
this._socket.on('reconnect_attempt', () => {
      this._socket.io.opts.transports = ['polling', 'websocket'];
});

On the backend I use feathers, on the frontend I use Angular.
Here is the error that shows up in Firefox:


If anyone is interested in checking, you can open leo.md in Firefox.
Does anyone know why sockets don't work on iOS and Firefox?

Thanks in advance for your replies, if any.

Answer 1

Thanks to Aleksey Ukolov , I found https://github.com/webcomponents/webcomponentsjs and solved the problem.
The sockets didn't work because there was another error.