Not sure what the problem is, Had to follow a few yt-bers one used tsc but had to switch to js completely.
2022-01-09T20:58:40.370270+00:00 app[worker.1]: /app/node_modules/discord.js/src/rest/APIRequest.js:33
2022-01-09T20:58:40.370282+00:00 app[worker.1]: agent ??= new https.Agent({ ...this.client.options.http.agent, keepAlive: true });
2022-01-09T20:58:40.370282+00:00 app[worker.1]: ^^^
2022-01-09T20:58:40.370283+00:00 app[worker.1]:
2022-01-09T20:58:40.370283+00:00 app[worker.1]: SyntaxError: Unexpected token '??='
2022-01-09T20:58:40.370284+00:00 app[worker.1]: at wrapSafe (internal/modules/cjs/loader.js:1001:16)
2022-01-09T20:58:40.370284+00:00 app[worker.1]: at Module._compile (internal/modules/cjs/loader.js:1049:27)
2022-01-09T20:58:40.370284+00:00 app[worker.1]: at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)
2022-01-09T20:58:40.370285+00:00 app[worker.1]: at Module.load (internal/modules/cjs/loader.js:950:32)
2022-01-09T20:58:40.370285+00:00 app[worker.1]: at Function.Module._load (internal/modules/cjs/loader.js:790:12)
2022-01-09T20:58:40.370286+00:00 app[worker.1]: at Module.require (internal/modules/cjs/loader.js:974:19)
2022-01-09T20:58:40.370286+00:00 app[worker.1]: at require (internal/modules/cjs/helpers.js:93:18)
2022-01-09T20:58:40.370286+00:00 app[worker.1]: at Object.<anonymous> (/app/node_modules/discord.js/src/rest/RESTManager.js:4:20)
2022-01-09T20:58:40.370287+00:00 app[worker.1]: at Module._compile (internal/modules/cjs/loader.js:1085:14)
2022-01-09T20:58:40.370287+00:00 app[worker.1]: at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)
2022-01-09T20:58:40.611984+00:00 heroku[worker.1]: State changed from up to crashed
SyntaxError: Unexpected token '??='
The version of Node.js you are using doesn't understand the nullish assignment operator, ??=. That operator was introduced at some point in the 15.x development cycle.
Ask Heroku to use Node 16 (or later) by including an engines section in your package.json, e.g.
{
"name": "Some Application",
"description": "An application that does cool stuff",
"version": "1.0.0",
"engines": {
"node": "16.x"
}
}