1. dotenv 配置

.env: Default. .env.local: Local overrides. This file is loaded for all environments except test. .env.development, .env.test, .env.production: Environment-specific settings. .env.development.local, .env.test.local, .env.production.local: Local overrides of environment-specific settings. Files on the left have more priority than files on the right:

npm start: .env.development.local, .env.development, .env.local, .env npm run build: .env.production.local, .env.production, .env.local, .env npm test: .env.test.local, .env.test, .env (note .env.local is missing)

必须是以REACT_APP开头的变量 才可以。