Registry / devops / metro-hermes-compiler

metro-hermes-compiler

library0.73.10jsnpmunverified

An experimental Node.js package providing a high-level API to interface with the Hermes bytecode compiler (HBC). Hermes is an open-source JavaScript engine optimized for React Native apps. This package integrates the compiler as a WebAssembly binary generated via Emscripten, enabling conversion of JavaScript/JSX into Hermes bytecode (.hbc) for improved startup performance on mobile. The current stable version is 0.73.10, with regular releases as part of Metro's release cadence (monthly minor updates). Unlike alternatives like Babel alone, this compiler is purpose-built for Hermes, producing optimized bytecode targeting React Native's Hermes runtime.

devops web-framework

npm install metro-hermes-compiler

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · METRO-HERMES-COMPI

metro-hermes-compiler

devopsjavascriptv0.73.10

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

compile

✓ import { compile } from 'metro-hermes-compiler'

Default and named exports are both available; ESM is primary.

default

✓ import { compile } from 'metro-hermes-compiler'

✗ import metroHermesCompiler from 'metro-hermes-compiler'

There is no default export; use named imports.

compileFromSource

✓ import { compileFromSource } from 'metro-hermes-compiler'

✗ const { compileFromSource } = require('metro-hermes-compiler')

CJS require is deprecated; use ESM imports.

Compiles a JavaScript file to Hermes bytecode using the compile function, with source map and optimization enabled.

import { compile } from 'metro-hermes-compiler'; import { readFileSync, writeFileSync } from 'fs'; const source = readFileSync('input.js', 'utf8'); const bytecode = compile(source, { sourceURL: 'input.js', sourceMap: true, optimize: true }); writeFileSync('output.hbc', bytecode); console.log('Compiled to Hermes bytecode.');

Debug

Known issues

breakingThe compile function now returns a Buffer instead of an object with a buffer property.

fix

Use compiled output directly as a Buffer instead of accessing .buffer.

affects: >=0.73.0

deprecatedThe 'compileFromSource' function has been deprecated in favor of 'compile'.

fix

Replace compileFromSource calls with compile and adjust parameters if needed.

affects: >=0.73.0

breakingNode.js versions below 14 are no longer supported.

fix

Upgrade Node.js to version 14 or later.

affects: >=0.70.0

gotchaThe WASM binary is large (~30MB) and may cause high memory usage during compilation.

fix

Ensure sufficient memory (at least 512MB heap) for the Node process.

affects: all

breakingOptions 'sourceMap' and 'optimize' were added as required; omitting them causes errors.

fix

Always include sourceMap and optimize boolean options in the config object.

affects: >=0.70.0

Errors

Common errors & fixes

Error: Can't resolve 'metro-hermes-compiler'

Package not installed or missing from node_modules.

fix

Run `npm install metro-hermes-compiler` or add it to package.json.

TypeError: compile is not a function

Incorrect import — using default export instead of named.

fix

Use `import { compile } from 'metro-hermes-compiler'` (not `import ... from` as default).

Module not found: Can't resolve 'metro-hermes-compiler' in '/path/to/project'

Webpack or bundler cannot locate the package; possibly not installed or incorrectly aliased.

fix

Ensure the package is installed and import path is correct (use 'metro-hermes-compiler' not a relative path).

Upgrade

Version history

0.73.10latest on npm

Audit

Dependencies

noderequiredRuns in Node.js; uses FileSystem and child_process APIs

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/facebook/metro ↗

packagehttps://www.npmjs.com/package/metro-hermes-compiler ↗

homepagehttps://metrobundler.dev ↗