js-async-handler

A lightweight async handler utility for Express.js middleware that automatically catches errors and passes them to the next middleware in the chain.

Features

• 🚀 Lightweight and fast
• 🔧 Works with both ES modules and CommonJS
• 💪 TypeScript support included
• 🛡️ Automatic error handling for async functions
• 📦 Zero dependencies

Installation

npm install js-async-handler

Usage

ES Modules

import { asyncHandler } from 'js-async-handler';
import express from 'express';

const app = express();

// Use with async route handlers
app.get('/users', asyncHandler(async (req, res) => {
  const users = await User.findAll(); // This can throw an error
  res.json(users);
}));

// Error will be automatically caught and passed to error middleware
app.use((err, req, res, next) => {
  console.error(err);
  res.status(500).json({ error: 'Internal Server Error' });
});

CommonJS

const { asyncHandler } = require('js-async-handler');
const express = require('express');

const app = express();

app.get('/users', asyncHandler(async (req, res) => {
  const users = await User.findAll();
  res.json(users);
}));

API

asyncHandler(fn)

Wraps an async function and automatically catches any errors, passing them to the Express error handler.

Parameters

• fn (Function): An async function that takes (req, res, next) as parameters

Returns

• (Function): Express middleware function

Example

const getUserById = asyncHandler(async (req, res) => {
  const user = await User.findById(req.params.id);
  if (!user) {
    return res.status(404).json({ error: 'User not found' });
  }
  res.json(user);
});

app.get('/users/:id', getUserById);

Why Use This?

Without asyncHandler, you need to manually catch errors in every async route:

// Without asyncHandler - repetitive try/catch
app.get('/users', async (req, res, next) => {
  try {
    const users = await User.findAll();
    res.json(users);
  } catch (error) {
    next(error);
  }
});

With asyncHandler, errors are automatically handled:

// With asyncHandler - clean and simple
app.get('/users', asyncHandler(async (req, res) => {
  const users = await User.findAll();
  res.json(users);
}));

TypeScript

This package includes TypeScript declarations. No need to install additional @types packages.

import { asyncHandler } from 'js-async-handler';
import { Request, Response } from 'express';

const getUsers = asyncHandler(async (req: Request, res: Response) => {
  const users = await User.findAll();
  res.json(users);
});

License

ISC

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.