Example 1: 'react-scripts' n’est pas reconnu en tant que commande interne ou externe, un programme exécutable ou un fichier de commandes. yarn upgrade //or npm update Example 2: 'react-scripts' is not recognized as an internal or external command, "scripts": { "build-css": "node-sass src/ -o src/", "build-js": "react-scripts build", "build": "npm run build-css && npm run build-js", "start-css": "npm run build-css && npm run build-css -- --watch --recursive", "start-js": "react-scripts start", "start": "npm-run-all -p start-css start-js", "test": "react-scripts test --env=jsdom", "eject": "react-scripts eject" },