CODEWITHSUNDEEP
javascriptnode.jsexpressmiddlewarehttp-status-codes
nook
nook

Reputation: 1884

Get response status code in a middleware

I am building an app in which I am trying to build my own logging system for each request.

For each request, I'd like to log the timestamp, the method used, the route, and finally the response code that has been sent to the client.

I have the following code for the moment :

// index.js
const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors');

const app = express();
app.use(bodyParser.json());
app.use(cors());

app.use(require('./lib/logging'));

app.get('/', (req, res, next) => {
  res.send('hello world !');
});

app.listen(3001);

// ./lib/logging.js
const moment = require('moment');
const chalk = require('chalk');
const log = console.log;

module.exports = (req, res, next) => {
  let now = `[${chalk.green(moment().format('HH:mm:ss'))}]`;
  let method = chalk.magenta(req.method);
  let route = chalk.blue(req.url);
  let code = chalk.yellow(res.statusCode); // Always 200
  log(`${now} ${method} request received on ${route} ${code}`);
  next();
}

Unfortunately, even if I do res.status(201).send('hello world') It will always catch a 200 status code... Is there a way to catch any response outgoing to the client and fetch its status code ?

Upvotes: 11

Views: 11062

Answers (4)

Alec
Alec

Reputation: 2762

The Express response extends the Node.js http.ServerResponse, so you can listen for the 'finish' event:

Event: 'finish'

Emitted when the response has been sent. More specifically, this event is emitted when the last segment of the response headers and body have been handed off to the operating system for transmission over the network. It does not imply that the client has received anything yet.

app.use((req, res, next) => {
  res.on('finish', () => {
    console.log(`Responded with status ${res.statusCode}`);
  });
  next();
});

Upvotes: 11

nook
nook

Reputation: 1884

Using the finish event from the response was indeed the good solution. The problem was in the finish event callback, I just couldn't use the arrow function because it wouldn't bind the this keyword, and this is were was stored the response data.

So the following code is working :

// ./lib/logging.js

const moment = require('moment');
const chalk = require('chalk');
const log = console.log;

module.exports = (req, res, next) => {
  let now = `[${chalk.green(moment().format('HH:mm:ss'))}]`;
  let method = chalk.magenta(req.method);
  let route = chalk.blue(req.url);
  res.on('finish', function() {
    let code = chalk.yellow(this.statusCode);
    log(`${now} ${method} request received on ${route} with code ${code}`);
  })

  next();
}

Upvotes: 22

Rahul Sharma
Rahul Sharma

Reputation: 10111

Create middleware and Override send function

app.use(function (req, res) {
    var send = res.send;
    res.send = function (body) {
        // Do something
        send.call(this, body);
    };
});

Upvotes: 2

shamon shamsudeen
shamon shamsudeen

Reputation: 5858

What I understand is you need to add some status codes in the response

You can simply set status codes like this

let code = {
   serverError:500,
   forbidden:401
}

res.status(code.serverError).json({
  message:'Server error'
})

If you want to set in the middleware

middleware.js

const statuscode = function middleware(req,res,next){


    let code = {
       serverError:500,
       forbidden:401
    }

    req.statusCode =code.serverError
   next()

}

module.exports = {
  statuscode
}

In the index.js

const middleware = require('./middleware');

app.get('/',middleware.statuscode, (req, res, next) => {
  console.log("Code from middleware",req.statusCode);
  res.send('hello world !');
});

Upvotes: 0

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