Prequisite:-

try npm run build to check if build script works or not locally.

server.js is present endpoint.

package.json
{
  "name": "server",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "server": "nodemon server.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
  ...
  },
  "devDependencies": {
   ...
  }
}
    


Open Heroku.
Connect to git repo.
Press Deploy Btn.