On server directory type:
npm i concurrently
{
"name": "billing",
"version": "1.0.0",
"description": "Facturacion MultiEmpresas",
"main": "server.js",
"scripts": {
"start": "node server.js","server": "nodemon server.js",
"client": "npm start --prefix client",
"clientinstall": "npm install --prefix client",
"dev": "concurrently \"npm run server\" \"npm run client\" "
}
"heroku-postbuild": "NPM_CONFIG_PRODUCTION=false npm install --prefix client && npm run build --prefix client"
(json file...)
(last line), <-- Don't forget the comma
"proxy":"http://localhost:5000" <- insert line
} <=last line
on server directory type
npm run dev