Resst

A simple yet powerful promises based REST API client with support for middlewares

Quick Start

const Resst = require("resst");
const backend = require("resst-fetch");

const api = new Resst({
    "host": "https://api.exemple.com/v1",
    "backend": backend,
});

api.get('/answers/42')
   .then(transaction => console.log(transaction))

Core concepts

Backend

The library itself can't fetch data, it relies on backends to handle the HTTP communication.

Backends are small wrappers that provide a unified way for Resst to allow the use of different HTTP clients. So far there are backends for :

• jquery: Easy and sure to use on client if your project already embed it
• fetch: The new native norm for Ajax calls, you will need a polyfill for older browser
• request: A popular lib for nodejs

Transaction

Rather than sending a request object and receiving a separated response object, Resst rely on a top level object called transaction which contains both request and response. This gives more context and is more consistent with the nature of HTTP.

Structure of the transaction object:

• request object
  • headers object (HTTP headers key value pairs)
  • body string
  • method string : HTTP method/verb, automatically set by according to the name of the called method
  • uri string Automatically set with the first argument of the called method
  • credentials string (ommit (default) | same-origin | include) according to fetch specification. Beware some backend wont' handle those parameters.
• response object
  • headers object (HTTP headers key value pairs)
  • status object
    • code int
    • message string
    • body string

Note that Resst doesn't process any body transformation for you (eg. JSON.parse), this is up to you but can be easily managed via middlewares.

middlewares

Resst is very light and unopiniated but brings you the flexibility of middlewares. There are two entrypoint for middlewares:

• Before sending the request
• After receiving the response

A middleware function receives two parameters, transaction and the next function to continue the process.

Exemples middlewares

// Alter request
function addCustomHeader(transaction, next) {
  if (transaction.request.method === 'POST') { // can read current values
    transaction.request.headers['X-foo'] = 'bar'; // can alter request
  }
  return next();
}


// Alter response
function parseJSON(transaction, next) {
  if (transaction.response.headers['content-type'] === 'application/json') {
    transaction.response.data = JSON.parse(transaction.response.body;
  }
  return next();
}

// Middlewares are passed to the middlewares property
const api = new Resst({
    host: 'https://api.exemple.com/v1',
    backend: backend,
    middlewares: {
      before: [
        addCustomHeader,
      ],
      after: [
        parseJSON,
      ],
    }
});

// Exemple of addng middleware after instanciation
// Here a simple logger
api.apply('before', function(transaction, next){
  console.log('Request about to be sent');
  console.log(transaction.request);
  return next();
});

api.get('/answers/42')
   .then(transaction => console.log(transaction))

Using the client

The client expose a method for get, post, put, patch, delete.

All these methods takes the same arguments (actually under the hood the same method is called with the HTTP verb already set).

• uri string
• request object (optional) properties will be merged to create the final request object to be passed to middlewares. You can basically override any part of the request.