Node.js deploys now run "build" script by default

Change effective on 11 March 2019

Node.js deployments now automatically execute an app’s build script if one is defined in the app’s package.json file.

"scripts": {
  "start": "node src/index.js",
  "build": "webpack" // This command will automatically run on deployment

If your app defines a build script that you don’t want to execute on Heroku, you can specify a heroku-postbuild script in your package.json file. If present, this script is executed instead of the build script.

For more information, please see the FAQ or our Node.js documentation.