Middleare component to send responses as JSON when requested as JSON

Usage no npm install needed!

<script type="module">
  import jsonMiddleware from 'https://cdn.skypack.dev/json-middleware';



Automatically send model data as JSON instead of passing to the view renderer when the user agent sends an Accept type of application/json or adds a json parameter to the query string.


Installing through npm is as easy as:

npm install json-middleware


To plug the middleware into a Connect or Express server:

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

When the middleware component runs, an isJson property is attached to the request. The value of the isJson property will either be true when the Accept header is set to application/json, or it will be set to whatever the json query string parameter value was.

To send a response as JSON instead of the usual view renderer, just call res.render as normal:

app.get('/', function(req, res) {
   res.render("index", myDataObject);

In this case, when the response is to be rendered as JSON, myDataObject will be sent as a JSON response instead of being passed to whatever view engine has been set up (eg: hogan-middleware)



app.get('/', function(req, res) {
   res.render("index", req.session); // render the index view with all data from the session

When accessing /, the index view is rendered with data held in the req.session object. Accessing /?json=on result in the req.session object being sent to the client as JSON and the console will print on.

Accessing / with the Accept request header set to application/json will result in the console printing true and the req.session object being sent to the client as JSON.


Only the req.render function is altered, all other utilities for responding to requests (eg: req.send) are left untouched.


Released under the MIT license. In short usage is free for any purpose, with the usual lack of warranties either explicit or implied.