Node.js + Express - How to log the request body and response body

Question

I have a small api I have built using Node.js and express. I am trying to create a logger and I need log the request body AND response body.

app.use((req, res) => {

    console.log(req);            

    res.on("finish", () => {

        console.log(res);

    });

});

"express": "^4.16.3",

However, i am not able to find the body in the req or res object. Please tell me how i can get them. thanks.

Answer 1

For res.body try the following snippet:

const endMiddleware = (req, res, next) => {
  const defaultWrite = res.write;
  const defaultEnd = res.end;
  const chunks = [];

  res.write = (...restArgs) => {
    chunks.push(new Buffer(restArgs[0]));
    defaultWrite.apply(res, restArgs);
  };

  res.end = (...restArgs) => {
    if (restArgs[0]) {
      chunks.push(new Buffer(restArgs[0]));
    }
    const body = Buffer.concat(chunks).toString('utf8');

    console.log(body);

    defaultEnd.apply(res, restArgs);
  };

  next();
};

app.use(endMiddleware)

// test
// HTTP GET /
res.status(200).send({ isAlive: true });

Answer 2

You need body-parser that will create body object for you in your request.
To do that npm install body-parser

var bodyParser = require('body-parser')//add this

app.use(bodyParser())//add this before any route or before using req.body

app.use((req, res) => {
  console.log(req.body); // this is what you want           

  res.on("finish", () => {

    console.log(res);

  });

});

Answer 3

Ran into this problem but didn't like the solutions. An easy way is to simply wrap the original res.send or res.json with your logger.

Put this as middleware before your routes.

app.use(function responseLogger(req, res, next) {
  const originalSendFunc = res.send.bind(res);
  res.send = function(body) {
    console.log(body);    // do whatever here
    return originalSendFunc(body);
  };
  next();
});

https://github.com/expressjs/express/blob/master/lib/response.js

res.send has signature of function(body) { return this; }