# body-parser — Request Body Parsing Middleware for Express

> The standard Node.js middleware for parsing incoming request bodies in Express applications, supporting JSON, URL-encoded, raw, and text content types.

## Install

Save as a script file and run:

# body-parser — Request Body Parsing Middleware for Express

## Quick Use
```bash
npm install body-parser
```
```js
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.post('/api/data', (req, res) => {
  console.log(req.body);
  res.json({ received: true });
});
```

## Introduction
body-parser is the de facto request body parsing middleware for Express and Connect-based Node.js applications. It reads the incoming request stream, parses the body based on the Content-Type header, and populates `req.body` with the result. While Express 4.16+ includes built-in equivalents (`express.json()` and `express.urlencoded()`), body-parser remains widely used for its additional parsers and fine-grained configuration options.

## What body-parser Does
- Parses JSON request bodies and populates `req.body` with the parsed object
- Parses URL-encoded form data with support for nested objects via `qs` library
- Parses raw binary bodies into a Buffer for webhook signatures and binary protocols
- Parses plain text bodies into a string
- Handles content encoding, size limits, and charset detection

## Architecture Overview
body-parser works by registering middleware functions that listen for specific Content-Type headers. When a matching request arrives, it reads the raw bytes from the request stream using the `raw-body` module, decompresses if gzip or deflate encoding is detected, then passes the bytes to the appropriate parser (JSON.parse, qs.parse, or identity). The parsed result is assigned to `req.body`. If parsing fails, it calls `next(err)` with a descriptive error. Each parser is a separate middleware function, so you mount only the parsers you need.

## Self-Hosting & Configuration
- Install via npm and require or import the package
- Mount `bodyParser.json()` for JSON APIs
- Mount `bodyParser.urlencoded({ extended: true })` for HTML form submissions
- Set `limit` option to control maximum body size (default 100KB for JSON)
- Use `type` option to parse custom Content-Types as JSON or URL-encoded

## Key Features
- JSON parser with `reviver` support and strict mode for arrays/objects only
- URL-encoded parser with `extended` mode using `qs` for nested object support
- Configurable size limits to prevent denial-of-service via oversized payloads
- Content encoding support for gzip and deflate compressed bodies
- `verify` callback for request body verification (useful for webhook signature checking)

## Comparison with Similar Tools
- **express.json() / express.urlencoded()** — built-in Express equivalents based on body-parser; body-parser offers raw and text parsers too
- **multer** — handles multipart/form-data for file uploads; body-parser handles JSON and URL-encoded only
- **co-body** — Koa-compatible body parser; body-parser is Express/Connect-specific
- **formidable** — full-featured multipart parser; body-parser focuses on non-file body types

## FAQ
**Q: Do I still need body-parser with Express 4.16+?**
A: For JSON and URL-encoded parsing, `express.json()` and `express.urlencoded()` are sufficient. Use body-parser if you need raw or text parsing, or want the `verify` callback.

**Q: How do I increase the body size limit?**
A: Pass `{ limit: '10mb' }` (or any size string) to the parser middleware.

**Q: How do I handle webhook signature verification?**
A: Use the `verify` option: `bodyParser.json({ verify: (req, res, buf) => { req.rawBody = buf; } })` to access the raw buffer for HMAC comparison.

**Q: Does it handle file uploads?**
A: No. body-parser does not handle multipart bodies. Use `multer` or `busboy` for file uploads.

## Sources
- https://github.com/expressjs/body-parser
- https://www.npmjs.com/package/body-parser

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Source: https://tokrepo.com/en/workflows/asset-4c0f30c8
Author: Script Depot