Running nested package.json commands

I am trying out digital ocean platform, have been using heroku; My project is a MEAN stack application. In heroku the build process worked like this; npm install the backend nodejs app; then that node app had a postinstall script that would run a required js script and also CD into my client directory and run the npm install for that directory, this client directory also had a post-install script to run ng build to build the angular repo for the nodejs to serve.

When I set up the repo to deploy to the DigitalOcean App Platform this nested npm install and commands do not seem to execute and build my frontend package.

I have been unable to find any questions or documents that reference this specific type of circumstance so I am hoping I am not asking an old question.