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0.2.5 • Public • Published


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An adapter to expose swatchjs via Express.

Quick start

The following exposes the simple API from the swatchjs's README file:

// Application server
const swatch = require('swatchjs');
const swatchExpress = require('swatchjs-express');
const model = swatch({
    "numbers.add": (a, b) => Number(a) + Number(b),
    "numbers.sub": (a, b) => Number(a) - Number(b),
const app = express();
swatchExpress(app, model);

That's it! No HTTP headers, status codes, or any other distracting verbiage. Each API method you declared can now be invoked using any of the supported HTTP verbs.

It is strongly advised that you only enable your APIs over HTTPS. Read more about HTTPS and why it's important and how to use HTTPS with your node server. This tutorial also provides a walkthrough of the entire process, including certificate setup and configuration.



The GET binding expects all parameters to be passed in the query string.

For instance, using the popular request package, you would invoke the numbers.add method above as follows:

// Client code (ex: Node server)
var request = require('request');

Every parameter in the query string is received as, well, a string. So if you plan on supporting the GET verb, it is recommended that either you provide parse functions for each of your arguments, or that you validate and coerce them inside your function (as shown in the example above).


The POST binding expects parameters to be passed in the body property of Express' request object.

Below is an example of calling the API using an XMLHttpRequest object:

// Client code (ex: Browser JS)
function post(url, body) {
    var request = new XMLHttpRequest();
    request.open('POST', url);
    request.setRequestHeader('Content-Type', 'application/json');
    return request;
var request = post(
        a: 1,
        b: 2,


Be mindful that how the body property of Express' request object gets populated depends on which body-parsing middleware you have enabled.

There are popular libraries for Express that enable the service to choose their behavior with regards to body parsing. A popular one is body-parser.

If you have a simple JSON body parser, then it will parse application/json content types, and your parameters could potentially have non-string types.

If, on the other hand, you have application/x-www-form-urlencoded parsing enabled, then all parameters will be strings, and the same considerations of the GET verb apply.

See the body-parser documentation for detailed instructions to use those and other options, or the documentation in the library of your choice.

Security Notice: Remember that you may receive string objects using either approach, which you should validate and coerce before passing to your handler functions.

// Application server
var express = require('express');
var bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.json()); // for parsing application/json
app.use(bodyParser.urlencoded({ extended: true })); // for parsing application/x-www-form-urlencoded

API reference

The swatchExpress function

// Application server
const swatchExpress = require('swatch-express');
swatchExpress(app, model, options);

Loading this library will result in a function (swatchExpress in the example above) which takes the following parameters:

Parameter Required Description
app Yes The Express app to populate.
model Yes The API model created by swatchjs.
options No Additional options when exposing the API. When present, must be an object.

The options object has the following properties:

Property Example Default value Description
verbs ['get'] ['get','post'] An array with a list of HTTP verbs to use. Each verb must be a string, and must be known.
prefix 'api' '' A URL prefix to be added to every route. For example, if the value of this option is 'product', then the URL of all APIs will start with /product/.


Coding Style

This project follows the AirBnB Javascript Coding Guidelines using ESLint settings.


npm i swatchjs-express

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