body-parser
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The body-parser package is a Node.js middleware that parses incoming request bodies before your handlers, available under the req.body property. It is commonly used to parse JSON, raw, text, and URL-encoded form data.
JSON Body Parsing
This feature allows the server to accept and parse incoming requests with JSON payloads, making the parsed data available under req.body.
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.json());
app.post('/json', (req, res) => {
res.send(req.body);
});URL-Encoded Form Data Parsing
This feature is used to parse payloads from forms submitted via HTTP POST. The 'extended' option allows for rich objects and arrays to be encoded into the URL-encoded format, allowing for a JSON-like experience with URL-encoded forms.
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.urlencoded({ extended: true }));
app.post('/form', (req, res) => {
res.send(req.body);
});Raw Body Parsing
This feature lets the server accept raw data in the request body, useful for parsing bodies that are not text-based, like binary data streams.
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.raw({ type: 'application/vnd.custom-type' }));
app.post('/raw', (req, res) => {
res.send(req.body);
});Text Body Parsing
This feature allows parsing text bodies, such as plain text or HTML, from the request body.
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.text({ type: 'text/html' }));
app.post('/text', (req, res) => {
res.send(req.body);
});Multer is a middleware for handling 'multipart/form-data', primarily used for uploading files. It is different from body-parser as it is specialized for file upload scenarios.
Formidable is a Node.js module for parsing form data, especially file uploads. It can handle multiple file uploads and supports file size limits, making it more feature-rich for handling forms than body-parser.
Busboy is a streaming parser for HTML form data for Node.js. It is faster and more efficient for large file uploads compared to body-parser, which does not handle file streams.
Designed for the Koa framework, koa-body is a full-featured body parser middleware. It supports multipart, urlencoded, and json request bodies and provides additional features like file uploads, making it a more comprehensive solution than body-parser for Koa applications.
Node.js body parsing middleware.
This does not handle multipart bodies, due to their complex and typically large nature. For multipart bodies, you may be interested in the following modules:
This module provides the following parsers:
Other body parsers you might be interested in:
$ npm install body-parser
var bodyParser = require('body-parser')
The bodyParser object exposes various factories to create middlewares. All
middlewares will populate the req.body property with the parsed body or
provide an error to the callback. The various errors are described in the
errors section.
Returns middleware that only parses json. This parser accepts any Unicode
encoding of the body and supports automatic inflation of gzip and deflate
encodings.
A new body object containing the parsed data is populated on the request
object after the middleware (i.e. req.body).
The json function takes an option options object that may contain any of
the following keys:
When set to true, then deflated (compressed) bodies will be inflated; when
false, deflated bodies are rejected. Defaults to true.
Controls the maximum request body size. If this is a number, then the value
specifies the number of bytes; if it is a string, the value is passed to the
bytes library for parsing. Defaults
to '100kb'.
The reviver option is passed directly to JSON.parse as the second
argument. You can find more information on this argument
in the MDN documentation about JSON.parse.
When set to true, will only accept arrays and objects; when false will
accept anything JSON.parse accepts. Defaults to true.
The type option is used to determine what media type the middleware will
parse. This option can be a function or a string. If a string, type option
is passed directly to the type-is
library and this can be an extension name (like json), a mime type (like
application/json), or a mime time with a wildcard (like */* or */json).
If a function, the type option is called as fn(req) and the request is
parsed if it returns a truthy value. Defaults to json.
The verify option, if supplied, is called as verify(req, res, buf, encoding),
where buf is a Buffer of the raw request body and encoding is the
encoding of the request. The parsing can be aborted by throwing an error.
Returns middleware that parses all bodies as a Buffer. This parser
supports automatic inflation of gzip and deflate encodings.
A new body object containing the parsed data is populated on the request
object after the middleware (i.e. req.body). This will be a Buffer object
of the body.
The raw function takes an option options object that may contain any of
the following keys:
When set to true, then deflated (compressed) bodies will be inflated; when
false, deflated bodies are rejected. Defaults to true.
Controls the maximum request body size. If this is a number, then the value
specifies the number of bytes; if it is a string, the value is passed to the
bytes library for parsing. Defaults
to '100kb'.
The type option is used to determine what media type the middleware will
parse. This option can be a function or a string. If a string, type option
is passed directly to the type-is
library and this can be an extension name (like bin), a mime type (like
application/octet-stream), or a mime time with a wildcard (like */* or
application/*). If a function, the type option is called as fn(req)
and the request is parsed if it returns a truthy value. Defaults to
application/octet-stream.
The verify option, if supplied, is called as verify(req, res, buf, encoding),
where buf is a Buffer of the raw request body and encoding is the
encoding of the request. The parsing can be aborted by throwing an error.
Returns middleware that parses all bodies as a string. This parser supports
automatic inflation of gzip and deflate encodings.
A new body string containing the parsed data is populated on the request
object after the middleware (i.e. req.body). This will be a string of the
body.
The text function takes an option options object that may contain any of
the following keys:
Specify the default character set for the text content if the charset is not
specified in the Content-Type header of the request. Defaults to utf-8.
When set to true, then deflated (compressed) bodies will be inflated; when
false, deflated bodies are rejected. Defaults to true.
Controls the maximum request body size. If this is a number, then the value
specifies the number of bytes; if it is a string, the value is passed to the
bytes library for parsing. Defaults
to '100kb'.
The type option is used to determine what media type the middleware will
parse. This option can be a function or a string. If a string, type option
is passed directly to the type-is
library and this can be an extension name (like txt), a mime type (like
text/plain), or a mime time with a wildcard (like */* or text/*).
If a function, the type option is called as fn(req) and the request is
parsed if it returns a truthy value. Defaults to text/plain.
The verify option, if supplied, is called as verify(req, res, buf, encoding),
where buf is a Buffer of the raw request body and encoding is the
encoding of the request. The parsing can be aborted by throwing an error.
Returns middleware that only parses urlencoded bodies. This parser accepts
only UTF-8 encoding of the body and supports automatic inflation of gzip
and deflate encodings.
A new body object containing the parsed data is populated on the request
object after the middleware (i.e. req.body). This object will contain
key-value pairs, where the value can be a string or array (when extended is
false), or any type (when extended is true).
The urlencoded function takes an option options object that may contain
any of the following keys:
The extended option allows to choose between parsing the URL-encoded data
with the querystring library (when false) or the qs library (when
true). The "extended" syntax allows for rich objects and arrays to be
encoded into the URL-encoded format, allowing for a JSON-like experience
with URL-encoded. For more information, please
see the qs library.
Defaults to true, but using the default has been deprecated. Please
research into the difference between qs and querystring and choose the
appropriate setting.
When set to true, then deflated (compressed) bodies will be inflated; when
false, deflated bodies are rejected. Defaults to true.
Controls the maximum request body size. If this is a number, then the value
specifies the number of bytes; if it is a string, the value is passed to the
bytes library for parsing. Defaults
to '100kb'.
The parameterLimit option controls the maximum number of parameters that
are allowed in the URL-encoded data. If a request contains more parameters
than this value, a 413 will be returned to the client. Defaults to 1000.
The type option is used to determine what media type the middleware will
parse. This option can be a function or a string. If a string, type option
is passed directly to the type-is
library and this can be an extension name (like urlencoded), a mime type (like
application/x-www-form-urlencoded), or a mime time with a wildcard (like
*/x-www-form-urlencoded). If a function, the type option is called as
fn(req) and the request is parsed if it returns a truthy value. Defaults
to urlencoded.
The verify option, if supplied, is called as verify(req, res, buf, encoding),
where buf is a Buffer of the raw request body and encoding is the
encoding of the request. The parsing can be aborted by throwing an error.
The middlewares provided by this module create errors depending on the error
condition during parsing. The errors will typically have a status property
that contains the suggested HTTP response code.
The following are the common errors emitted, though any error can come through for various reasons.
This error will occur when the request had a Content-Encoding header that
contained an encoding but the "inflation" option was set to false. The
status property is set to 415.
This error will occur when the request is aborted by the client before reading
the body has finished. The received property will be set to the number of
bytes received before the request was aborted and the expected property is
set to the number of expected bytes. The status property is set to 400.
This error will occur when the request body's size is larger than the "limit"
option. The limit property will be set to the byte limit and the length
property will be set to the request body's length. The status property is
set to 413.
This error will occur when the request's length did not match the length from
the Content-Lentgh header. This typically occurs when the requst is malformed,
typically when the Content-Length header was calculated based on characters
instead of bytes. The status property is set to 400.
This error will occur when something called the req.setEncoding method prior
to this middleware. This module operates directly on bytes only and you cannot
call req.setEncoding when using this module. The status property is set to
500.
This error will occur when the request had a charset parameter in the
Content-Type header, but the iconv-lite module does not support it OR the
parser does not support it. The charset is contained in the message as well
as in the charset property. The status property is set to 415.
This error will occur when the request had a Content-Encoding header that
contained an unsupported encoding. The encoding is contained in the message
as well as in the encoding property. The status property is set to 415.
This example demonstrates adding a generic JSON and URL-encoded parser as a top-level middleware, which will parse the bodies of all incoming requests. This is the simplest setup.
var express = require('express')
var bodyParser = require('body-parser')
var app = express()
// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: false }))
// parse application/json
app.use(bodyParser.json())
app.use(function (req, res) {
res.setHeader('Content-Type', 'text/plain')
res.write('you posted:\n')
res.end(JSON.stringify(req.body, null, 2))
})
This example demonstrates adding body parsers specifically to the routes that need them. In general, this is the most recommend way to use body-parser with express.
var express = require('express')
var bodyParser = require('body-parser')
var app = express()
// create application/json parser
var jsonParser = bodyParser.json()
// create application/x-www-form-urlencoded parser
var urlencodedParser = bodyParser.urlencoded({ extended: false })
// POST /login gets urlencoded bodies
app.post('/login', urlencodedParser, function (req, res) {
if (!req.body) return res.sendStatus(400)
res.send('welcome, ' + req.body.username)
})
// POST /api/users gets JSON bodies
app.post('/api/users', jsonParser, function (req, res) {
if (!req.body) return res.sendStatus(400)
// create user in req.body
})
All the parsers accept a type option which allows you to change the
Content-Type that the middleware will parse.
// parse various different custom JSON types as JSON
app.use(bodyParser.json({ type: 'application/*+json' }))
// parse some custom thing into a Buffer
app.use(bodyParser.raw({ type: 'application/vnd.custom-type' }))
// parse an HTML body into a string
app.use(bodyParser.text({ type: 'text/html' }))
FAQs
Node.js body parsing middleware
The npm package body-parser receives a total of 29,201,370 weekly downloads. As such, body-parser popularity was classified as popular.
We found that body-parser demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 2 open source maintainers collaborating on the project.
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