Compose HTTP clients using JavaScript's fetch API
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README.md

http-client Travis npm package

http-client lets you compose HTTP clients using JavaScript's fetch API. This library has the following goals:

  • Preserve the full capabilities of the fetch API
  • Provide an extendable middleware API
  • Use the same API on both client and server

Installation

Using npm:

$ npm install --save http-client

http-client requires you to bring your own global fetch function (for convenience when using the top-level createFetch function). isomorphic-fetch is a great polyfill if you need to support environments that don't already have a global fetch function.

Then, use as you would anything else:

// using ES6 modules
import { createFetch } from 'http-client'

// using CommonJS modules
var createFetch = require('http-client').createFetch

The UMD build is also available on unpkg:

<script src="https://unpkg.com/http-client/umd/http-client.min.js"></script>

You can find the library on window.HTTPClient.

Usage

http-client simplifies the process of creating flexible HTTP clients that work in both node and the browser. You create your own fetch function using the createFetch method, optionally passing middleware as arguments.

import { createFetch, base, accept, parse } from 'http-client'

const fetch = createFetch(
  base('https://api.stripe.com/v1'),  // Prefix all request URLs
  accept('application/json'),         // Set "Accept: application/json" in the request headers
  parse('json')                       // Read the response as JSON and put it in response.body
)

fetch('/customers/5').then(response => {
  console.log(response.jsonData)
})

Top-level API

createFetch(...middleware)

Creates a fetch function that uses some middleware. Uses the global fetch function to actually make the request.

createStack(...middleware)

Combines several middleware into one, in the same order they are provided as arguments. Use this function to create re-usable middleware stacks or if you don't want to use a global fetch function.

enableRecv(fetch)

Returns an "enhanced" version of the given fetch function that knows how to run response handlers registered using recv. This is only really useful when using stacks directly instead of createFetch.

Middleware

http-client provides a variety of middleware that may be used to extend the functionality of the client. Out of the box, http-client ships with the following middleware:

accept(contentType)

Adds an Accept header to the request.

import { createFetch, accept } from 'http-client'

const fetch = createFetch(
  accept('application/json')
)

auth(value)

Adds an Authorization header to the request.

import { createFetch, auth } from 'http-client'

const fetch = createFetch(
  auth('Bearer ' + oauth2Token)
)

base(baseURL)

Adds the given baseURL to the beginning of the request URL.

import { createFetch, base } from 'http-client'

const fetch = createFetch(
  base('https://api.stripe.com/v1')
)

fetch('/customers/5') // GET https://api.stripe.com/v1/customers/5

body(content, contentType)

Sets the given content string as the request body.

import { createFetch, body } from 'http-client'

const fetch = createFetch(
  body(JSON.stringify(data), 'application/json')
)

debug()

Adds a debug property to the response or error object so you can inspect them. Mainly useful for testing/debugging (should run after all other middleware).

import { createFetch, debug } from 'http-client'

const fetch = createFetch(
  // ... other middleware
  debug()
)

fetch(input).then(response => {
  console.log(response.debug.input, response.debug.options)
})

header(name, value)

Adds a header to the request.

import { createFetch, header } from 'http-client'

const fetch = createFetch(
  header('Content-Type', 'application/json')
)

init(propertyName, value)

Sets the value of an arbitrary property in the options object.

import { createFetch, init } from 'http-client'

const fetch = createFetch(
  init('credentials', 'include')
)

json(object)

Adds the data in the given object as JSON to the request body.

method(verb)

Sets the request method.

import { createFetch, method } from 'http-client'

const fetch = createFetch(
  method('POST')
)

params(object)

Adds the given object to the query string of GET/HEAD requests and as a x-www-form-urlencoded payload on all others.

import { createFetch, method, params } from 'http-client'

// Create a client that will append hello=world to the URL in the query string
const fetch = createFetch(
  params({ hello: 'world' })
)

// Create a client that will send hello=world as POST data
const fetch = createFetch(
  method('POST'),
  params({ hello: 'world' })
)

parse(parser, as = 'body')

Reads the response body to completion, parses the response, and puts the result on response.body (or whatever as is). parser must be the name of a valid Body parsing method. The following parsers are available in the spec:

  • arrayBuffer
  • blob
  • formData
  • json
  • text
import { createFetch, parse } from 'http-client'

const fetch = createFetch(
  parse('json')
)

fetch(input).then(response => {
  console.log(response.body)
})

Note: Some parsers may not be available when using a fetch polyfill. In particular if you're using node-fetch, you should be aware of its limitations.

query(object)

Adds the data in the given object (or string) to the query string of the request URL.

recv(handler)

Used to handle the response in some way. The handler function should return the new response value, or a promise for it. Response handlers run in the order they are defined.

import { createFetch, recv } from 'http-client'

const fetch = createFetch(
  recv(response => (console.log('runs first'), response)),
  recv(response => (console.log('runs second'), response))
)

Stacks

Middleware may be combined together into re-usable middleware "stacks" using createStack. A stack is itself a middleware that is composed of one or more other pieces of middleware. Thus, you can pass a stack directly to createFetch as if it were any other piece of middleware.

This is useful when you have a common set of functionality that you'd like to share between several different fetch methods, e.g.:

import { createFetch, createStack, header, base, parse, query } from 'http-client'

const commonStack = createStack(
  header('X-Auth-Key', key),
  header('X-Auth-Email', email),
  base('https://api.cloudflare.com/client/v4'),
  parse('json')
)

// This fetch function can be used standalone...
const fetch = createFetch(commonStack)

// ...or we can add further middleware to create another fetch function!
const fetchSinceBeginningOf2015 = createFetch(
  commonStack,
  query({ since: '2015-01-01T00:00:00Z' })
)

Stacks are also useful when you don't have a global fetch function, e.g. in node. In those cases, you can still use http-client middleware and supply your own fetch (we recommend node-fetch) function directly, but make sure you "enhance" it first:

const { createStack, enableRecv, header, base } = require('http-client')

// We need to "enhance" node-fetch so it knows how to
// handle responses correctly. Specifically, enableRecv
// gives a fetch function the ability to run response
// handlers registered with recv (which parse, used below,
// uses behind the scenes).
const fetch = enableRecv(
  require('node-fetch')
)

const stack = createStack(
  header('X-Auth-Key', key),
  header('X-Auth-Email', email),
  base('https://api.cloudflare.com/client/v4'),
  parse('json')
)

stack(fetch, input, options)