I have to create the frontend for an application. Someone else created the backend using node. I have always created my projects using create-react-app, however, since the backend is already created, including modules, routes, db, etc, I couldn't use this command to create the project, so I installed all my packages independently. This is my package.json:
{
  "name": "test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "build-css": "node-sass-chokidar client/ -o client/",
    "watch-css": "npm run build-css && node-sass-chokidar client/ -o client/ --watch --recursive",
    "start-js": "react-scripts start",
    "build": "npm run build-css && react-scripts build",
    "test": "react-scripts test --env=jsdom",
    "eject": "react-scripts eject",
    "start": "npm-run-all -p start-node watch-css start-js",
    "start-node": "node index.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "axios": "^0.16.2",
    "body-parser": "^1.18.2",
    "bulma": "^0.6.0",
    "express": "^4.16.2",
    "mongoose": "^4.12.3",
    "morgan": "^1.9.0",
    "q": "^1.4.1",
    "react": "^16.0.0",
    "react-dom": "^16.0.0",
    "react-router": "^4.2.0",
    "react-router-dom": "^4.2.2",
    "react-scripts": "^1.0.14"
  },
  "devDependencies": {
    "node-sass-chokidar": "0.0.3",
    "npm-run-all": "^4.1.1",
    "sass": "^1.0.0-beta.2"
  }
}
There's a problem with the start-js since node is already runnin on port 3000 and react needs to run as well. How can I make both run concurrently?
 
    