npm install --save-dev babel-preset-expo babel-loader

{ "presets": ["@babel/preset-env", "@babel/preset-react"] }

"scripts": { "start": "react-native start", "build": "react-native bundle --platform ios --entry-file index.ios.js --dev false --bundle-output ios/main.jsbundle --assets-dest ios", "test": "jest", "lint": "eslint ." }