- /MyApp
  - /ios
  - data.json
  - index.ios.js

{
  "words": [
    {"word": "xxx", "done": false} // and more...
  ]
}

var RNFS = require('react-native-fs');
 // create a path you want to write to
 var path = RNFS.DocumentDirectoryPath + '/test.txt';

// write the file
RNFS.writeFile(path, 'Lorem ipsum dolor sit amet', 'utf8')
.then((success) => {
 console.log('FILE WRITTEN!');
})
.catch((err) => {
 console.log(err.message);
});