having trouble deploying reactapp to heroku code example

Example 1: create react app deployment heroku

npm install -g create-react-app
create-react-app my-app
cd my-app
git init
heroku create -b https://github.com/mars/create-react-app-buildpack.git
git add .
git commit -m "react-create-app on Heroku"
git push heroku master
heroku open

Example 2: react scrip for deplot heroku

"scripts": { 
  "dev": "react-scripts 
  "start", "start": "serve -s build", 
  "build": "react-scripts build", 
  "test": "react-scripts test --env=jsdom",
  "eject": "react-scripts eject", 
  "heroku-postbuild": "npm run build" 
},