Class constructor Controller cannot be invoked without 'new' (3.0.0-beta1)

Just had a go at updating our Stimulus 2.x app to the beta. We’re using Rails/Webpacker.

I think there’s some missing parts of the docs around this change (in the push to importmaps) so I did have to guess some of the new Webpack configuration code. Namely - definitionsFromContext used to come from stimulus/webpack-helpers and I think it now comes from just @hotwired/stimulus.

import { Application } from "@hotwired/stimulus";
import { definitionsFromContext } from "@hotwired/stimulus";

const application = Application.start();
const context = require.context("./controllers", true, /\.js$/);
application.load(definitionsFromContext(context));

This runs, however in the browser I get the following error - following the stacktrace it occurs in each of my controller modules.

Uncaught (in promise) TypeError: Class constructor Controller cannot be invoked without 'new'
    at new _default (application.js:3048)
    at new extended (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:1338)
    at new Context (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:1198)
    at Module.fetchContextForScope (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:1400)
    at Module.connectContextForScope (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:1386)
    at Router.scopeConnected (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:1705)
    at ScopeObserver.elementMatchedValue (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:1623)
    at ValueListObserver.tokenMatched (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:814)
    at TokenListObserver.tokenMatched (vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:747)
    at vendors-node_modules_babel_runtime_regenerator_index_js-node_modules_hotwired_stimulus_dist_s-68817b.js:741

Nothing fancy going on with my controllers - just updated the import from stimulus to @hotwired/stimulus as expected.

import { Controller } from "@hotwired/stimulus";

export default class extends Controller {
  //
}

[m3xq]

In package.json add "not IE 11" to "browserslist"

"browserslist": [
    "defaults",
    "not IE 11"
  ]

[dwightwatson]

@m3xq’s suggestion appears to have done the trick for me.