Nifty worker/client postMessage utility
Made with ❤ at @outlandish
Makes communication between a client and service worker super easy...
- Send messages from
client -> worker
andworker -> client
with one call tochannel.send()
- Simple API: send anonymous data-only messages or a typed message with data
- Register handlers for typed messages and anonymous messages
- Easily respond to any message by calling
respond()
in the handler - Receive a response for a message using the familiar Promise
then()
method
// ES6
import msgr from 'msgr'
// CommonJS
var msgr = require('msgr')
// RequireJS
define(['msgr'], function (msgr) {/*...*/})
<!-- Script, available as `window.msgr` -->
<script src="/node_modules/msgr/index.js"></script>
Client: msgr.client()
Pass in reference to the worker and a collection of message handlers:
const recipient = navigator.serviceWorker.controller
const channel = msgr.client(recipient, {
// Predefined message handlers
SAY_HELLO: (data) => console.log('Hello, ' + data) //=> 'Hello, World!'
})
// Send something "unknown" to the worker.
// Notice it does not have a tag.
channel.send({
username: 'Flanders',
location: 'Springfield'
})
// Send a "known" message to the worker
channel.send('CACHE_ASSET', '/cat.gif').then(function (message) {
console.log(message) //=> 'Caching complete!'
})
Worker: msgr.worker()
On the worker you just pass in your message handlers:
const channel = msgr.worker({
CACHE_ASSET: cacheAsset
})
channel.receive(function (data) {
// Do something with an "unknown" message
// that does not have a predefined handler.
console.log(data) //=> { username: 'Flanders', ... }
})
// Send something "known" to the client using a tag.
channel.send('SAY_HELLO', 'World!')
function cacheAsset (url, respond) {
doCaching().then(function () {
respond('Caching complete!')
})
}
Initialise a msgr
client.
- serviceWorker {ServiceWorkerRegistration} Worker that will receive messages sent via channel
- handlers {Object} An object of message type/handler mappings
Returns a Channel. See the Channel API Docs for more details.
Example:
msgr.client(navigator.serviceWorker.controller, {
NOTIFY: function (respond) {
new Notification('You have a notification!')
respond('GOT_THE_NOTIFICATION')
}
})
Initialise a msgr
worker.
- handlers {Object} An object of message type/handler mappings
Returns a Channel. See the Channel API Docs for more details.
Example:
msgr.worker({
NOTIFY: function (respond) {
new Notification('You have a notification!')
respond('GOT_THE_NOTIFICATION')
}
})
Register a handler to be called when the channel is opened between client and worker.
- handler {Function} The ready handler
Although you can register ready handlers, you can send messages before the channel is open using
channel.send()
and these will be queued and sent as soon as the channel is ready.
Example:
channel.ready(function () {
application.start()
})
Send a message through the channel to the worker/client.
- [type] {String} (optional) The message type
- data {Any} The message data
Returns a Message. See the Message API Docs for more details.
If data
is not a string it will be stringified by calling data.toString()
.
If called before the channel is ready the message will be queued and sent as soon as the channel is open.
Example:
// Tagged
channel.send('NOTIFY_USER', { message: 'Update complete' })
// Untagged
channel.send('This is the untagged data')
Handle an "unknown" message that is not tagged.
- handler {Function} The message handler
The handler receives two arguments: the data
of the message and a respond
function.
Example:
channel.receive(function (data, respond) {
console.log('Got some unknown data: ' + data)
})
Register a handler to receive the response to a message.
- handler {Function} Response handler
Example:
// In client message handlers
msgr({
NOTIFY_USER: function (data, respond) {
new Notification('Job ' + data.id + ' was completed')
respond('From worker: job deleted') // ACK
}
})
// In worker
channel.send('NOTIFY_USER', { id: 1337 }).then((data) => {
console.log(data) //=> 'From worker: job deleted'
})
Send a response to a received message.
This function is passed as the second argument to both "known" and "unknown" message handlers.
- [data] {Any} (optional) The data to respond to the message with
All pull requests and issues welcome!
If you're not sure how, check out Kent C. Dodds' great video tutorials on egghead.io!
msgr
was created by Sam Gluck and is released under the MIT license.