Metro Bundler

0.0.1 verified Sat Apr 25 auth: no javascript deprecated

Metro is the JavaScript bundler for React Native, designed for sub-second reload cycles, fast startup, and quick bundling speeds. It handles thousands of modules in a single application and is integrated with every React Native project out of the box. Version 0.0.1 appears to be a fork (prn-metro-bundler) of the original Facebook metro-bundler, but the npm package seems to be a placeholder or mis-published. The original metro-bundler was previously part of the react-native repository and is now maintained separately. Note: The correct npm package for the official Metro bundler is 'metro' (or 'metro-bundler' as an alias), but the version 0.0.1 shown here is likely a test/published fork from a Chinese company (pinguo-zhangzhi).

Common errors

error Cannot find module 'metro-bundler' ↓

cause The package 'metro-bundler' is deprecated and not available on npm (only historical).

fix

Install 'metro' instead: npm install metro

error require('metro-bundler') returns undefined ↓

cause Metro v0.50+ switched to ESM only; CommonJS require does not work.

fix

Use ES module import: import Metro from 'metro'

Warnings

gotcha This package (prn-metro-bundler v0.0.1) is a fork from pinguo-zhangzhi and is likely not the official Metro bundler. Use the official 'metro' package instead. ↓

fix Install 'metro' from npm: npm install metro

deprecated The official metro-bundler package is deprecated; use 'metro' instead. ↓

fix Replace 'metro-bundler' with 'metro' in package.json and imports.

breaking In Metro v0.50+, the API changed from default export to named exports. Old code using `const Metro = require('metro-bundler')` will break. ↓

fix Use named imports: `import { createServer } from 'metro'`.

Install

npm install prn-metro-bundler

yarn add prn-metro-bundler

pnpm add prn-metro-bundler

Imports

Metro
wrong
```
const Metro = require('metro')
```
correct
```
import Metro from 'metro'
```
ESM-only; CommonJS require is not supported for metro package since v0.55.
runBuild
wrong
```
import { runBuild } from 'metro-bundler'
```
correct
```
import { runBuild } from 'metro'
```
runBuild is not exported from 'metro-bundler'; use 'metro' instead.

createServer

wrong

const createServer = require('metro-bundler').createServer

correct

import { createServer } from 'metro'

Use 'metro' package; 'metro-bundler' is an alias but not recommended.

Quickstart

Creates a Metro bundler server alongside an Express app, demonstrating basic use of Metro's server creation.

import Metro from 'metro';
import express from 'express';

const app = express();
const port = process.env.PORT || 8081;

// Start Metro bundler server
Metro.createServer().then(server => {
  server.listen(port, () => {
    console.log(`Metro bundler running on port ${port}`);
  });
});

app.get('/', (req, res) => {
  res.send('Hello from Metro bundler');
});

app.listen(3000, () => {
  console.log('Express server listening on port 3000');
});