finalhandler

finalhandler

Node.js function to invoke as the final step to respond to HTTP request.

Installation

This is a Node.js module available through the npm registry. Installation is done using the npm install command:

$ npm install finalhandler

API

const finalhandler = require('finalhandler')

finalhandler(req, res, [options])

Returns function to be invoked as the final step for the given req and res. This function is to be invoked as fn(err). If err is falsy, the handler will write out a 404 response to the res. If it is truthy, an error response will be written out to the res or res will be terminated if a response has already started.

When an error is written, the following information is added to the response:

• The res.statusCode is set from err.status (or err.statusCode). If this value is outside the 4xx or 5xx range, it will be set to 500.
• The res.statusMessage is set according to the status code.
• The body will be the HTML of the status code message if env is 'production', otherwise will be err.stack.
• Any headers specified in an err.headers object.

The final handler will also unpipe anything from req when it is invoked.

options.env

By default, the environment is determined by NODE_ENV variable, but it can be overridden by this option.

options.onerror

Provide a function to be called with the err when it exists. Can be used for writing errors to a central location without excessive function generation. Called as onerror(err, req, res).

Examples

always 404

const finalhandler = require('finalhandler')
const http = require('http')

const server = http.createServer((req, res) => {
  const done = finalhandler(req, res)
  done()
})

server.listen(3000)

perform simple action

const finalhandler = require('finalhandler')
const fs = require('fs')
const http = require('http')

const server = http.createServer((req, res) => {
  const done = finalhandler(req, res)

  fs.readFile('index.html', (err, buf) => {
    if (err) return done(err)
    res.setHeader('Content-Type', 'text/html')
    res.end(buf)
  })
})

server.listen(3000)

use with middleware-style functions

const finalhandler = require('finalhandler')
const http = require('http')
const serveStatic = require('serve-static')

const serve = serveStatic('public')

const server = http.createServer((req, res) => {
  const done = finalhandler(req, res)
  serve(req, res, done)
})

server.listen(3000)

keep log of all errors

const finalhandler = require('finalhandler')
const fs = require('fs')
const http = require('http')

const server = http.createServer((req, res) => {
  const done = finalhandler(req, res, { onerror: logerror })

  fs.readFile('index.html', (err, buf) => {
    if (err) return done(err)
    res.setHeader('Content-Type', 'text/html')
    res.end(buf)
  })
})

server.listen(3000)

function logerror (err) {
  console.error(err.stack || err.toString())
}

License

MIT

Similar packages

Other packages similar to finalhandler

on-finished

The 'on-finished' package is similar to finalhandler in that it is used to execute a callback when a HTTP response is finished or when an error occurs. It is a lower-level utility than finalhandler and does not handle the response itself, but rather provides a way to detect when the response has been completed.

connect

Connect is an extensible HTTP server framework for node, which uses 'middleware' to enhance Node.js features. While not a direct alternative to finalhandler, it includes similar error handling and final response capabilities within its middleware stack.