Express sets body to Cannot GET [route] while asynchronous code is being executed #4965

askenderski · 2022-08-05T09:47:45Z

askenderski
Aug 5, 2022

I have an express application with some articles stored in a Mongo database. While I'm waiting for the mongoose model Article to load, the body of the request is changed to:

<!DOCTYPE html>
<html lang="en">
    
<head>
	<meta charset="utf-8">
    	<title>Error</title>
</head>
    
<body>
  	<pre>Cannot GET /articles</pre>
</body>
    
</html>

and the status code to 404. The code I'm using to see the body being sent is this:

function logResponseBody(req, res, next) {
    var oldWrite = res.write,
       oldEnd = res.end;
      
    var chunks = [];
      
    res.write = function (chunk) {
         chunks.push(new Buffer(chunk));
    
         res.body = Buffer.concat(chunks).toString('utf8');
      
         oldWrite.apply(res, arguments);
    };
      
    res.end = function (chunk) {
          if (chunk) chunks.push(new Buffer(chunk));
          
          res.body = Buffer.concat(chunks).toString('utf8');
          
          oldEnd.apply(res, arguments);
    };
      
    next();
}
      
module.exports = logResponseBody;

It's a slightly modified version of this one: https://stackoverflow.com/a/34712950/13300387

My code is this:

route

router.get("/", async (req, res, next) => {
    console.log(res.body); //undefined
    console.log(res.statusCode); //200
    const articles = await ArticleModel.find();
    console.log(res.body); //...Cannot GET /articles...
    console.log(res.statusCode); //404
    
    res.status(200).json(articles);
});

model

const mongoose = require('mongoose');
    
const Schema = mongoose.Schema;
    
const ArticleSchema = new Schema({
    title: {
        type: String,
        required: true,
        unique: true
    },
    description: {
        type: String,
        required: true
    },
    type: {
        type: String,
        required: true
    }
}, {collection: "articles"});
    
const ArticleModel = mongoose.model('article', ArticleSchema);
    
module.exports = ArticleModel;

I have posted this same question on Stack Overflow (https://stackoverflow.com/questions/73237206/express-sets-body-to-cannot-get-route-while-asynchronous-code-is-being-execute) but I did not get an answer and cannot think of how to modify it to be more concise or clear.

elrefai99 · 2025-09-13T21:47:05Z

elrefai99
Sep 13, 2025

res.body is undefined until it is actually sent and is not present in the get method.

The HTML Cannot GET /articles comes from a different request (e.g. browser auto-requesting favicon.ico or hitting a non-matching route), not from your route itself.

To fix it

Log before sending JSON directly:

const articles = await ArticleModel.find();
console.log("Sending:", articles);
res.status(200).json(articles);

Move logging into your middleware after res.end:

res.end = function (chunk) {
  if (chunk) chunks.push(Buffer.from(chunk));
  res.body = Buffer.concat(chunks).toString('utf8');
  console.log("Final response body:", res.body);
  oldEnd.apply(res, arguments);
};

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elrefai99 Sep 13, 2025

To fix it

askenderski
Aug 5, 2022

elrefai99
Sep 13, 2025