Fixing the "Compiling JS Failed" Error in Expo React Native for Android When Loading Big JSON Files

Understanding and Fixing "Compiling JS Failed" Error in Expo React Native

Developing mobile applications with React Native and Expo offers a powerful way to create cross-platform apps, but issues can arise when handling large data files, especially on Android. One common error developers encounter is the "Compiling JS failed" message. This typically happens when trying to load extensive JSON files.

While the app may work perfectly in a web environment, Android often presents challenges due to differences in how it processes and compiles JavaScript files. The specific error related to invalid UTF-8 byte sequences can be frustrating, as it points to a problem with the file's encoding or the way the JavaScript is compiled.

In this article, we will explore potential solutions to the "Compiling JS failed" error, including how to validate JSON files, manage large datasets, and address UTF-8 encoding issues that may be causing this problem. We’ll walk through several debugging steps to help you identify and fix the underlying issue.

By following these guidelines, you should be able to resolve the error and improve the performance of your Expo React Native app on Android devices. Let's dive into the key techniques and troubleshooting strategies that will help you get your app back on track.

Handling Large JSON Files in Expo React Native and Optimizing Performance

The scripts provided above address the common issue of handling large JSON files in an Expo React Native app, particularly when it runs on Android. The first approach focuses on using AsyncStorage to store and retrieve JSON data in smaller chunks, preventing memory overload during runtime. By splitting the large JSON file into chunks and storing them asynchronously, the script ensures that the app doesn't attempt to load the entire file into memory at once, which could lead to the "Compiling JS failed" error on Android devices.

In the useEffect hook, the script initiates the chunk loading process by calling a function that iterates through the JSON data in defined parts. Each chunk is saved using AsyncStorage, a local storage solution for React Native. Once all the data is stored, the function retrieves these chunks and merges them into one continuous dataset that can be rendered inside a ScrollView component. This method ensures that the app remains responsive, as it avoids large memory operations and handles data in smaller, more manageable portions.

The second script provides a backend solution using Node.js and streams to handle the large JSON file. By leveraging fs.createReadStream(), the JSON file is read piece by piece and sent to the client via an HTTP response. This approach optimizes server-side performance, as the entire file is not loaded into memory. The server-side streaming method is particularly effective when delivering large datasets over the network, ensuring that data is sent in chunks to prevent performance bottlenecks and minimize memory usage.

In summary, both solutions aim to tackle the core issue of handling large files in an Expo React Native app. The first method addresses performance on the client side by using local storage to split and load data incrementally, while the second focuses on server-side optimization using streaming. These techniques are essential for preventing common errors such as "Compiling JS failed" and ensure that the app can handle large data without crashing or significantly impacting performance on Android devices.

import React, { useEffect, useState } from 'react';
import { ScrollView, StyleSheet, Text } from 'react-native';
import AsyncStorage from '@react-native-async-storage/async-storage';
import baghawyJSON from '@/assets/tafaseer/baghawy.json';
const CHUNK_SIZE = 1000; // Adjust the size as needed
export default function LargeJSONHandler() {
  const [data, setData] = useState([]);
  const loadChunkedJSON = async () => {
    try {
      for (let i = 0; i < baghawyJSON.length; i += CHUNK_SIZE) {
        const chunk = baghawyJSON.slice(i, i + CHUNK_SIZE);
        await AsyncStorage.setItem(`chunk_${i}`, JSON.stringify(chunk));
      }
      // After storing, retrieve and set data
      const storedData = [];
      for (let i = 0; i < baghawyJSON.length; i += CHUNK_SIZE) {
        const chunk = await AsyncStorage.getItem(`chunk_${i}`);
        storedData.push(JSON.parse(chunk));
      }
      setData(storedData.flat());
    } catch (error) {
      console.error("Error loading JSON data:", error);
    }
  };
  useEffect(() => {
    loadChunkedJSON();
  }, []);
  return (
    <ScrollView style={styles.scrollView}>
      {data.map((item, index) => (
        <Text key={index}>{item.text}</Text>
      ))}
    </ScrollView>
  );
}
const styles = StyleSheet.create({
  scrollView: { padding: 20 },
});

const express = require('express');
const fs = require('fs');
const app = express();
const port = 3000;
app.get('/large-json', (req, res) => {
  const readStream = fs.createReadStream('./largeData.json');
  res.setHeader('Content-Type', 'application/json');
  readStream.pipe(res);
});
app.listen(port, () => {
  console.log(`Server running on port ${port}`);
});
// To handle the JSON in the app, fetch the data in chunks using a streaming client.

Handling Large Files and Preventing UTF-8 Errors in Expo React Native

One of the major challenges developers face when building mobile apps with Expo React Native is managing large data files, especially JSON files. These files can often lead to performance bottlenecks, especially on Android devices, where memory management differs significantly from the web. The issue you are encountering, such as "Compiling JS failed" and "Invalid UTF-8 continuation byte," usually stems from improper file encoding or mishandling of large data sets during the app compilation process.

Apart from using chunking methods, ensuring that all JSON files are properly encoded in UTF-8 is critical. If any part of the file contains characters that are not recognized by the UTF-8 standard, Android devices may throw errors during compilation. Therefore, validating your JSON files for hidden characters or incorrect encodings is an essential step before attempting to load them into your application. This validation ensures smooth loading across platforms.

Another strategy involves dynamically loading the JSON files only when necessary, as opposed to loading all data at the start. By using lazy loading and pagination techniques, you can optimize how data is displayed without overwhelming the device's memory. These methods help minimize the chances of running into performance issues, while ensuring the app remains responsive even with large data sets. Exploring these techniques will significantly improve app stability and efficiency on Android devices.