How to properly debug javascript in the browser?

Question

JavaScript

I used to write small applications for the site and used webpack devserver, proxying requests from the main server to dev and I had a hot reload there.
part of the config

devServer: {
        port: 3001,

        host: 'localhost',
        proxy: {
            "*": {
                target:"https://proect.local:80",
                secure: false
            }
        }
    },

Everything works well, no need to constantly press f5.
Now I started writing applications for Bitrix24 (CRM corporate portal) with the old version of Bitrix the config worked (I added only port 443).
Under the current version, it does not proxy requests, it says that 404.
There are also applications that open in an iframe (the application runs in it)
What are the debugging tools so that you do not have to constantly reload the page through f5 who can encounter such a problem?