what is the purpose of express res.get(field) method?

June 28, 2022

I saw some code examples about using express res.get(field)

Is it for debugging purpose or there are other use cases for it?

the code examples I saw looks like this :

var express = require('express');
var app = express();
var PORT = 3000;

// Defining an endpoint
app.get('/api', function(req, res){

   // Setting the Content-type
   res.set({
      'Content-Type': 'application/json',
   });

   // "text/plain"
   console.log(res.get('Content-Type'));
   res.end();
});

app.listen(PORT, function(err){
   if (err) console.log(err);
   console.log("Server listening on PORT", PORT);
});

when hitting the end point the output :

application/json; charset=utf-8

>Solution :

Express uses this method internally to check if particular headers are set, typically to set a default if they aren’t or to augment them (for instance, in your example you set the Content-Type header to application/json, and Express appended ; charset=utf-8 to it).

You could imagine situations where a request handler wants to see if a particular middleware (perhaps a third-party one) set a particular header and/or a particular value, and adjust the way it handles the final response.