Sadly, the method posted by Scoooolzs stopped working after a recent webpack update.

Here's the new working code:

(webpackChunkdiscord_app.push([[''],{},e=>{m=[];for(let c in e.c)m.push(e.c[c])}]),m).find(m=>m?.exports?.default?.getToken!==void 0).exports.default.getToken()

You can find a library in this repo to hook into Discord clients' functions.

(Community edit:)

Prettified:

(

    webpackChunkdiscord_app.push(

        [

            [''],

            {},

            e => {

                m=[];

                for(let c in e.c)

                    m.push(e.c[c])

            }

        ]

    ),

    m

).find(

    m => m?.exports?.default?.getToken !== void 0

).exports.default.getToken()