file-exist-react-native-FileSystem-API.js

import { Platform, NativeModules } from 'react-native';

const { FileSystem } = NativeModules;

const path = `${FileSystem.documentDirectory}/myFile.txt`;

FileSystem.getInfo(path)
  .then(stats => {
    if (stats.exists) {
      console.log('File exists');
    } else {
      console.log('File does not exist');
    }
  })
  .catch(error => {
    console.log(error);
  });