fetch-sync

> Proxy fetch requests through the Background Sync API

Made with ❤ at @outlandish

![js-standard-style](http://standardjs.com/)

Fetch Sync allows you to proxy fetch requests through the Background Sync API so that they are
honoured if made when the UA is offline! Hooray!

Check out a live demo here.

- Make requests offline that will be sent when the UA regains connectivity (even if the web page is no longer open).
- Responses are forwarded back to the client as soon as they are received.
- Implements a familiar fetch-like API: similar function signature and the same return type (a Response).
- Make named requests that have their response stored in an IDBStore which you can collect in subsequent user sessions.
- Manage sync operations with fetchSync.{get,getAll,cancel,cancelAll}().
- Can be used with existing Service Worker infrastructures with importScripts, or handles SW registration for you.
- If the browser does not support Background Sync, the library will fall back on normal fetch requests.

Install

sh

npm install fetch-sync --save





Table of Contents



- Requirements

- Support

- __Import__

- __Initialisation__

- __Usage__

- __Sync API__

- Dependencies

- Test

- Development

- Contributing

- Author & License



Requirements



The library utilises some new technologies so currently only works in some browsers. It definitely works in

Chrome Canary

with the

experimental-web-platform-features

 flag enabled.



The browser must support:



- Background Sync

- Service Worker

- Fetch

- IndexedDB

- [Promise] (https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise)



Support



Chrome Canary | Chrome | Firefox | IE | Opera | Safari

:------------:|:------:|:-------:|:--:|:-----:|:-----:

✔             |✔      |✘       |✘   |✘     |✘



Initialise



__Existing Service Worker__



If your application already uses a Service Worker, you can import the fetch-sync worker using

importScripts

js

importScripts('node_modules/fetch-sync/dist/fetch-sync.sw.min.js')





And then call

fetchSync.init()

 somewhere in your application's initialisation procedure.



__No Service Worker__



fetch-sync can handle registration if you don't use a SW already...



Either serve the fetch-sync worker file with a header

"Service-Worker-Allowed : /"

, or to avoid configuring headers,

create a Service Worker script in the root of your project and use the method above for 'Existing Service Worker'.



Then see the example under Usage for the

fetchSync.init()

 method.



Import



__Client__

js

// ES6

import fetchSync from 'fetch-sync'

js

// CommonJS

var fetchSync = require('fetch-sync')

html





__Worker__



See Initialise for details on importing and registering the service worker.



Usage



$3



Initialise fetchSync.



- __options__ {Object} _(optional)_ options object



Look at the documentation for

sw-register



available options and for more details on Service Worker registration.



Example:

js

// Import client lib...



// ES6

import fetchSync from 'fetch-sync'



// ES5

var fetchSync = require('fetch-sync')

html

js

// Initialise, passing in worker lib location...



fetchSync.init({

  url: 'node_modules/fetch-sync/dist/fetch-sync.sw.js',

  scope: '' // e.g. 'http://localhost:8000'

})





$3



Perform a

sync

 Background Sync operation.



- [__name__] {String} _(optional)_ name of the sync operation

- __request__ {String|Request} URL or an instance of fetch Request

- [__options__] {Object} _(optional)_ fetch options object



Returns a Promise that resolves on success of the fetch request. Rejects if a sync exists with this name already.



If called with a

name

:



- the response will be stored and can be retrieved later using e.g.

fetchSync.get('name').then(sync => sync.response)

.

- the response will not automatically be removed from the IDBStore in the worker. You should request

that a named sync be removed manually by using

sync.remove()

.

- see the Sync API for more details.



Examples:



- named GET

js

    fetchSync('GetMessages', '/messages')

      .then((response) => response.json())

      .then((json) => console.log(json.foo))





- unnamed POST

js

    const post = fetchSync('/update-profile', {

      method: 'POST',

      body: { name: '' }

    })



    // cancel the sync...

    post.cancel()





- unnamed with options

js

    const headers = new Headers();



    headers.append('Authorization', 'Basic abcdefghijklmnopqrstuvwxyz');



    //

fetchSync accepts the same args as fetch

...

    fetchSync('/send-message', { headers })





- named with options

js

    fetchSync('/get-messages', { headers })





- unnamed with Request

js

    fetchSync(

      new Request('/messages')

    )





$3



Get a sync by its name.



- __name__ {String} name of the sync operation to get



Returns a Promise that resolves with success of the sync operation or reject if sync operation is not found.



There are also some properties/methods on the Sync. See the Sync API for more details.



Example:

js

fetchSync('SendMessage', '/message', { body: 'Hello, World!' })



const sync = fetchSync.get('SendMessage')



sync.then((response) => {

  if (response.ok) {

    alert(

Your message was received at ${new Date(sync.syncedOn).toDateString()}.



  } else {

    alert('Message failed to send.')

  }

})





$3



Get all sync operations.



Returns an array of all sync operations (named and unnamed).



Example:

js

fetchSync.getAll()

  .then((syncs) => syncs.forEach(sync => sync.cancel()))





$3



Cancel the sync with the given

name

.



- __name__ {String} name of the sync operation to cancel



Example:

js

fetchSync('Update', '/update', { body })

fetchSync.cancel('Update')





$3



Cancel all syncs, named and unnamed.



Sync API



$3



Cancels the sync operation.



Returns a Promise of success of the cancellation.



Example:

js

const sync = fetchSync.get('Update')

sync.cancel()





$3



The unique ID of the sync operation. This will be its name if it has one.



$3



The name of the sync operation if it has one.



$3



The time that the sync operation was created.



$3



The time that the sync operation was completed.



$3



Is the sync operation cancelled?



Dependencies



- idb-wrapper

- msgr

- sw-register

- serialise-request

- serialise-response

- mini-defer



Test



As the library depends on Service Workers and no headless browser has (good enough) support for Service Workers

that would allow tests to be executed within the console, tests are ran through the browser using

Mocha and Chai.



On running

npm test an Express server will be started at localhost:8000

.



Run the tests:

sh

$ cd fetch-sync

$ npm test





Development



The library is bundled by Webpack

and transpiled by Babel.



- Install dependencies:

npm install



- Start Webpack in a console:

npm run watch



- Start the test server in another:

npm test



- Navigate to

http://localhost:8000





Contributing



All pull requests and issues welcome!



If you're not sure how, check out Kent C. Dodds'

great video tutorials on egghead.io!



Author & License

fetch-sync` was created by Sam Gluck and is released under the MIT license.

fetch-sync

> Proxy fetch requests through the Background Sync API

Made with ❤ at @outlandish

Install

sh

npm install fetch-sync --save





Table of Contents



- Requirements

- Support

- __Import__

- __Initialisation__

- __Usage__

- __Sync API__

- Dependencies

- Test

- Development

- Contributing

- Author & License



Requirements



The library utilises some new technologies so currently only works in some browsers. It definitely works in

Chrome Canary

with the

experimental-web-platform-features

 flag enabled.



The browser must support:



- Background Sync

- Service Worker

- Fetch

- IndexedDB

- [Promise] (https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise)



Support



Chrome Canary | Chrome | Firefox | IE | Opera | Safari

:------------:|:------:|:-------:|:--:|:-----:|:-----:

✔             |✔      |✘       |✘   |✘     |✘



Initialise



__Existing Service Worker__



If your application already uses a Service Worker, you can import the fetch-sync worker using

importScripts

js

importScripts('node_modules/fetch-sync/dist/fetch-sync.sw.min.js')





And then call

fetchSync.init()

 somewhere in your application's initialisation procedure.



__No Service Worker__



fetch-sync can handle registration if you don't use a SW already...



Either serve the fetch-sync worker file with a header

"Service-Worker-Allowed : /"

, or to avoid configuring headers,

create a Service Worker script in the root of your project and use the method above for 'Existing Service Worker'.



Then see the example under Usage for the

fetchSync.init()

 method.



Import



__Client__

js

// ES6

import fetchSync from 'fetch-sync'

js

// CommonJS

var fetchSync = require('fetch-sync')

html





__Worker__



See Initialise for details on importing and registering the service worker.



Usage



$3



Initialise fetchSync.



- __options__ {Object} _(optional)_ options object



Look at the documentation for

sw-register



available options and for more details on Service Worker registration.



Example:

js

// Import client lib...



// ES6

import fetchSync from 'fetch-sync'



// ES5

var fetchSync = require('fetch-sync')

html

js

// Initialise, passing in worker lib location...



fetchSync.init({

  url: 'node_modules/fetch-sync/dist/fetch-sync.sw.js',

  scope: '' // e.g. 'http://localhost:8000'

})





$3



Perform a

sync

 Background Sync operation.



- [__name__] {String} _(optional)_ name of the sync operation

- __request__ {String|Request} URL or an instance of fetch Request

- [__options__] {Object} _(optional)_ fetch options object



Returns a Promise that resolves on success of the fetch request. Rejects if a sync exists with this name already.



If called with a

name

:



- the response will be stored and can be retrieved later using e.g.

fetchSync.get('name').then(sync => sync.response)

.

- the response will not automatically be removed from the IDBStore in the worker. You should request

that a named sync be removed manually by using

sync.remove()

.

- see the Sync API for more details.



Examples:



- named GET

js

    fetchSync('GetMessages', '/messages')

      .then((response) => response.json())

      .then((json) => console.log(json.foo))





- unnamed POST

js

    const post = fetchSync('/update-profile', {

      method: 'POST',

      body: { name: '' }

    })



    // cancel the sync...

    post.cancel()





- unnamed with options

js

    const headers = new Headers();



    headers.append('Authorization', 'Basic abcdefghijklmnopqrstuvwxyz');



    //

fetchSync accepts the same args as fetch

...

    fetchSync('/send-message', { headers })





- named with options

js

    fetchSync('/get-messages', { headers })





- unnamed with Request

js

    fetchSync(

      new Request('/messages')

    )





$3



Get a sync by its name.



- __name__ {String} name of the sync operation to get



Returns a Promise that resolves with success of the sync operation or reject if sync operation is not found.



There are also some properties/methods on the Sync. See the Sync API for more details.



Example:

js

fetchSync('SendMessage', '/message', { body: 'Hello, World!' })



const sync = fetchSync.get('SendMessage')



sync.then((response) => {

  if (response.ok) {

    alert(

Your message was received at ${new Date(sync.syncedOn).toDateString()}.



  } else {

    alert('Message failed to send.')

  }

})





$3



Get all sync operations.



Returns an array of all sync operations (named and unnamed).



Example:

js

fetchSync.getAll()

  .then((syncs) => syncs.forEach(sync => sync.cancel()))





$3



Cancel the sync with the given

name

.



- __name__ {String} name of the sync operation to cancel



Example:

js

fetchSync('Update', '/update', { body })

fetchSync.cancel('Update')





$3



Cancel all syncs, named and unnamed.



Sync API



$3



Cancels the sync operation.



Returns a Promise of success of the cancellation.



Example:

js

const sync = fetchSync.get('Update')

sync.cancel()





$3



The unique ID of the sync operation. This will be its name if it has one.



$3



The name of the sync operation if it has one.



$3



The time that the sync operation was created.



$3



The time that the sync operation was completed.



$3



Is the sync operation cancelled?



Dependencies



- idb-wrapper

- msgr

- sw-register

- serialise-request

- serialise-response

- mini-defer



Test



As the library depends on Service Workers and no headless browser has (good enough) support for Service Workers

that would allow tests to be executed within the console, tests are ran through the browser using

Mocha and Chai.



On running

npm test an Express server will be started at localhost:8000

.



Run the tests:

sh

$ cd fetch-sync

$ npm test





Development



The library is bundled by Webpack

and transpiled by Babel.



- Install dependencies:

npm install



- Start Webpack in a console:

npm run watch



- Start the test server in another:

npm test



- Navigate to

http://localhost:8000





Contributing



All pull requests and issues welcome!



If you're not sure how, check out Kent C. Dodds'

great video tutorials on egghead.io!



Author & License

fetch-sync` was created by Sam Gluck and is released under the MIT license.