A demonstration of using content negotiation to render browsable Web APIs in Node.js / Express.

Web APIs that can render as HTML when accessed in a web browser present a more usable, universal, and accessible interface.

The Django REST framework project is a current example of this, but I believe that it would be beneficial to see the practice extend into other languages and frameworks.

This project demonstrates creating a Web browsable API in Node.js, using the Express micro-framework.

The components we require in order to achieve this:

• A content negotiation middleware that renders either text/html or application/json depending on the client Accept header.
• A template for rendering the HTML responses, along with API controls.
• The ajax-form library for supporting method and content type overriding on HTML forms.

Clone the repository, install the dependancies, and start the server:

git clone git@github.com:tomchristie/express-browsable-api.git
cd express-browsable-api
npm install
node server.js

The service will now be running on http://127.0.0.1:3000

The example server will respond to any route, returning information on the request method, headers, and any JSON content in the request body, if it exists.

Make an HTTP request using curl, and the server will return a JSON response:

$ curl 127.0.0.1:3000
{
    "method": "GET",
    "headers": {
        "user-agent": "curl/7.28.1",
        "host": "127.0.0.1:3000",
        "accept": "*/*"
    },
    "body": {}
}

Enter the same URL in the browser, and the server will return HTML, including the rendered JSON content, along with controls for making further requests to the API.

If using the Express browsable API in your own project, you need to use the res.sendData() method in your routes, rather than the usual res.send().

The content negotiation middleware will then render the data into either JSON or HTML, as appropriate.

For example, use this:

res.sendData({'hello': 'world'})

And not this:

req.send(JSON.stringify({'hello': 'world'}))

Some thoughts on extending the functionality of the project…

• Use API schemas or similar to generate appropriate HTML form inputs for any given endpoint instead of the free-form JSON input.
• Use the the response Allow header to determine which methods to display.
• Add support for authentication headers to be set be the client which are persisted across requests.
• Render the application response headers in the HTML content.
• Hyperlink any URLs in the HTML content or relation headers to enhance the browsability of APIs that use hyperlinked resources.

Copyright © 2015, Tom Christie All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

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