Heroku Unexpected Token ??=

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2021-12-02T02:42:45.888858+00:00 app[worker.1]: /app/node_modules/discord.js/src/rest/APIRequest.js:33
2021-12-02T02:42:45.888875+00:00 app[worker.1]:     agent ??= new https.Agent({ ...this.client.options.http.agent, keepAlive: true });
2021-12-02T02:42:45.888876+00:00 app[worker.1]:           ^^^
2021-12-02T02:42:45.888876+00:00 app[worker.1]: 
2021-12-02T02:42:45.888877+00:00 app[worker.1]: SyntaxError: Unexpected token '??='

I am receiving this error while trying to start a fresh Discord.JS v13 heroku bot.

My Procfile states: worker: node src/index.js

I have added my .env and configured how the bot starts, instead of using npm start. As you can probably deduce, I do not have a ??= anywhere in my code. How can I fix this issue?

discord.js node.js heroku javascript
1 Answers

The error is coming from discord.js and it's because you're using an older version of node.js. The logical nullish assignment operator (??=) is only available in node v15+.

Heroku says that "if a Node version isn’t specified in the engine, the 14.x release will be used". You can add an engines prop to your package.json file to specify the version of node.js. As discord.js v13 requires node.js v16.6+, you can add the following:

  "engines": {
    "node": "16.6"
  }

Or to request the latest v16, add this:

  "engines": {
    "node": "16.x"
  }
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