NodeJS Express = Catch the sent status code in the response

Question

I'm using NodeJS with Express middleware, and my only issue is to catch the exact Sent status Code to the response (for logs) in a global function.

Using the following code :

const express = require('express');
const bodyParser = require('body-parser');

const app = express();
const router = express.Router();

app.use(bodyParser.json());

router.get('/', (req, res, next) => {
 // ..... SOME LOGIC
 // Suppose that the variable content is coming from the DB
 if (content.length === 0)
 {
    // Status Code : 404
    res.send(404).send("The product cannot be found");
 }
 // Status Code : 200
 res.json(content);
});

app.use((req, res, next) => {
  // Problem : Always returns 200 !
  console.log(res.statusCode);
  next();
});

I am trying to catch all the requests, to log the status code in a middleware (app.use), but my problem is that the res.statusCode is always returning 200, even when I send myself a 404.

Question :

How can I catch the exact sent Status Code in a global function so that I can log it?

Thank you.

Answer 1

Alternatively, if you don't want to do next(new Error), you can use res.on("finish",.... Which is the last event which fires, wrapping your code in that will yield the correct statusCode

const express = require("express");
const bodyParser = require("body-parser");

const app = express();
const router = express.Router();

app.use(bodyParser.json());

router.get("/", (req, res, next) => {
  //presume 404
  res.send(404).send("The product cannot be found");
});

app.use((req, res, next) => {
  res.on("finish", function() {
    console.log(res.statusCode); // actual 404
  });

  console.log(res.statusCode); // 200 :/ so dont use
  next();
});

app.listen();

Answer 2

you might want to try something like below - use the next callback to pass control to the error handler middleware:

  router.get('/', ( req, res, next) => {
     // ......... SOME LOGIC
     // Suppose that the variable content is coming from the DB
     if (content.length === 0) {
      const err = new Error('The product cannot be found');
      err.status = 404;
      next(err);
     }
     res.json(content);
  });

  app.use((err,req, res, next) => {
    console.log(err.status);
  });