Today I learned a new trick. The method. req.is On every object there is a method called that allows you to check if the incoming request’s is a certain . Express request is “Content-Type” HTTP header mime type If you want to check the mime of a request, just use the method as so: var express = require(‘express’); var app = express(); // listening for post requests on the root. app.post(‘/’, (req, res, next) => { console.log( req.is(‘*/*’), req.is(‘text/*’), req.is(‘*/html’), req.is(‘json’), req.is(‘*/json’) ); res.sendStatus(200); }); app.listen(3300); If you put the above snippet in a file and run it with (you’ll need to have the express package installed), and then make the following request: index.js node index.js curl curl http://localhost:3300 -H “Content-Type: application/json” -d ‘body’ You’ll get the following output: req.is(‘*/*’) --> 'application/json' req.is(‘text/*’) --> false req.is(‘*/html’) --> false req.is(‘json’) --> 'json' req.is(‘*/json’) --> 'application/json' On changing the content-type to text/html, you get: req.is(‘*/*’) --> 'text/html' req.is(‘text/*’) --> 'text/html' req.is(‘*/html’) --> 'text/html' req.is(‘*/json’) --> false It’s pretty simple to see what’s happening here. If the content-type matches on the extension name ( ) or a mime type ( ) or a mime type wildcard ( ), that name/mime type will be returned. json application/json */json The method accepts an array of inputs or multiple inputs (which then get picked from arguments and pushed into an array) and returns the first matching input against the content-type or false. So with incoming content-type set to text/html: req.is(‘text/html’, 'text') --> 'text/html' But: req.is(‘text’, 'text/html') --> 'text' All this functionality comes from Express’s usage of the library. type-is Pretty neat stuff.
