Devour JSON-API Client

– "Don't just consume your JSON-API, Devour it"

The JSON API specification has given us a sensible convention to build our API's against. It's flexible, well thought out, and comes fully loaded with clear answers to questions like pagination, filtering, sparse fields, and relationships.

While JSON API is amazing, it can be painful to work with if you don't have a good consumer library. It turns out that serializing and deserializing JSON API resources manually is quite painful. Enter Devour...

Another Implementation?

While there are quite a few JavaScript client implementations, none of them appeared to offer the exact feature set we needed with the simplicity we required.

Quick Start

// npm install devour-client --save

// Import
import JsonApi from 'devour-client'

// Bootstrap
const jsonApi = new JsonApi({apiUrl:'http://your-api-here.com'})

// Define Model
jsonApi.define('post', {
  title: '',
  content: '',
  tags: []
})

// To find many...
jsonApi.findAll('post')

// To find many with filters...
jsonApi.findAll('post', {page: {number: 2}})

// To find one...
jsonApi.find('post', 5)

// To create...
jsonApi.create('post', {
  title: 'hello',
  content: 'some content',
  tags: ['one', 'two']
}, {
  include: 'tags'
})

// To update...
jsonApi.update('post', {
  id: 5,
  title: 'new title',
  content: 'new content',
  tags: ['new tag']
}, {
  include: 'tags'
})

// To destroy...
jsonApi.destroy('post', 5)

// To make arbitrary requests through the middleware stack
jsonApi.request('https://example.com', 'GET', { a_query_param: 3 }, { some_payload_item: 'blah' })

Initializer

const jsonApi = new JsonApi({apiUrl: 'http://your-api-here.com'})

Devour takes an object as the initializer. The following options are available:

apiUrl: The HTTP API end point, for example: http://your-api-here.com

middleware: An array of middleware to use. See below

logger: A boolean to enable or disable the logger. (Default: true)

pluralize: A function like pluralize, or false to disable pluralization. (Default: require('pluralize'))

resetBuilderOnCall: A boolean to clear the builder stack after a .get, .post, .patch, .destroy call. (Default: true)

auth: An object with username and password, used to pass in HTTP Basic Authentication Headers, new JsonApi({apiUrl: 'http://your-api-here.com', auth: {username: 'secret', password: 'cheesecake'})

trailingSlash: An optional object to use trailing slashes on resource and/or collection urls (defaults to false), new JsonApi({apiUrl: 'http://your-api-here.com', trailingSlash: {resource: false, collection: true})

Relationships

Devour comes stock with an easy way of defining relationships which can be included when hitting your API.

jsonApi.define('post', {
  title: '',
  content: '',
  comments: {
    jsonApi: 'hasMany',
    type: 'comments'
  }
})

jsonApi.define('comment', {
  comment: ''
})

let { data, errors, meta, links } = jsonApi.findAll('post', {include: 'comments'})
// => data.comment will be populated with any comments included by your API

Flexibility

Devour uses a fully middleware based approach. This allows you to easily manipulate any part of the request and response cycle by injecting your own middleware. In fact, it's entirely possible to fully remove our default middleware and write your own. Moving forward we hope to see adapters for different server implementations. If you'd like to take a closer look at the middleware layer, please checkout:

• The index.js file where we construct our default middleware stack
• The middleware folder that contains all our default JSON API middleware

Your First Middleware

Adding your own middleware is easy. It's just a simple JavaScript object that has a name, req, and/or res property. The req or res property is a function that receives a payload, which houses all the details of the request cycle (see documentation below). For async operations, your req or res methods can return a promise, which will need to resolve before the middleware chain continues. Otherwise, you may just manipulate the payload as needed and return it immediately.

let requestMiddleware = {
  name: 'add-cats-to-request',
  req: (payload)=> {
    if(payload.req.method === 'GET') {
      payload.req.cats = 'more-cats'
    }
    return payload
  }
}

let responseMiddleware = {
  name: 'only-cats-please',
  res: (payload) => {
    payload.res.data = ['Cats', 'Cats', 'Cats']
    return payload
  }
}

let errorMiddleware = {
  name: 'nothing-to-see-here',
  error: function (payload) {
    return { errors: [] }
  }
}

jsonApi.insertMiddlewareBefore('axios-request', requestMiddleware)
jsonApi.insertMiddlewareAfter('response', responseMiddleware)
jsonApi.replaceMiddleware('errors', errorMiddleware)

The payload object

The payload object that gets passed to your middleware function has the following shape:

• data - JSON data contained in request/response body
• headers - An object containing the headers for the request/response
• method - A string representing the HTTP verb used, e.g. 'GET' or 'PATCH'
• model - The model that initiated this request
• params - An object containing the keys/values passed in the query params of the request
• url - The URL to which the request was sent

The payload for response middleware contains these additional fields:

• config - An object of low-level config data
• request - The original XMLHttpRequest object used to make the request
• status - HTTP status code for the request, e.g. 200
• statusText - Text representation of the HTTP status, e.g. "OK", "Created"

Your Second Middleware

This request middleware may be handy for live queries as it permits the last pending request to be cancelled (via Axios request cancellation feature).

let cancellableRequest = {
    name: 'axios-cancellable-request',
    req: function (payload) {
        let jsonApi = payload.jsonApi
        return jsonApi.axios(payload.req, {
            cancelToken: new jsonApi.axios.CancelToken(function executor(c) {
                // An executor function receives a cancel function as a parameter
                jsonApi.cancel = c;
            })
        })
    }
}

jsonApi.replaceMiddleware('axios-request', cancellableRequest)

// jsonApi.cancel() will cancel the last pending request

Options

When declaring a model you may pass in a few extra options. We will likely expand these options as we find new and interesting requirements.

jsonApi.define('product', {
  title: '',
  description: ''
  price: ''
}, {
  readOnly: ['price'],
  collectionPath: 'awesome-products',
  serializer: (rawItem)=> {
    return {customStuff: true}
  },
  deserializer: (rawItem)=> {
    return {customStuff: true}
  }
})

There are also a few options we can set on the jsonApi instance directly. For example:

// Append headers to every request
jsonApi.headers['my-auth-token'] = 'xxxxx-xxxxx'
// Replace the default middleware stack with your own
jsonApi.middleware = [{...}, {...}, {...}]
// Change the apiUrl
jsonApi.apiUrl = 'http://api.yoursite.com'

URL Builder

JSON API Specs allows nested URLs to be used to define a resource. For example, /authors/1/posts may define posts from author with ID 1.

The builder pattern allows arbitrary nested URL construction by chaining .one(model, id) and .all(model) and append an action, one of: .get, .post, .patch and .destroy

For example:

let jsonApi = new JsonApi({apiUrl: 'http://api.yoursite.com'})
jsonApi.define('author', {name: ''})
jsonApi.define('post', {title: ''})

jsonApi.one('author', 1).all('post').get({include: 'books'}) // GET http://api.yoursite.com/authors/1/posts?include=books
jsonApi.one('author', 1).all('post').post({title:'title'}, {include: 'books'}) // POST http://api.yoursite.com/authors/1/posts?include=books

Polymorphic Relationships

To specify a polymorphic relationship, simply define a model with a polymorphic relationship without specifying its type.

jsonApi.define('order', {
  name: '',
  payables: {
    jsonApi: 'hasMany'
  }
})

let payables = [{id: 4, type: 'subtotal'}, {id: 5, type: 'tax'}]
let { data, errors, meta, links } = jsonApi.all('order').post({ name: 'first', payables })
/* => POST http://api.yoursite.com/orders
{
  type: orders,
  attributes: {
    name: 'first'
  },  
  relationships: {
    payables: {
      data: [
        { id: 4, type: 'subtotal' },
        { id: 5, type: 'tax' }
      ]
    }
  }
} */

Migrating from Devour v1.x

For convenience, Devour v1.x would simply return the deserialized data as the response.

jsonApi.define('post', {
  title: '',
  content: ''
})

let post = jsonApi.findAll('post')
// => post.title will be populated with the title returned by your API

Devour v2.x focuses on meeting the requirements of the JSON API specification which introduces a bit more complexity out of necessity. In addition to the deserialized collection or resource data, the response contains document level errors, meta, and links information as well.

jsonApi.define('post', {
  title: '',
  content: ''
})

let { data, errors, meta, links } = jsonApi.findAll('post')
// => data.title will be populated with the title returned by your API
// => errors will be populated with any errors returned by your API
// => meta will be populated with any meta data returned by your API
// => links will be populated with any document level links returned by your API