A tiny RPC library that works on windows, iframes, WebWorkers and ServiceWorkers.
TL;DR: With Comlink you can work on objects from another JavaScript realm
(like a Worker or an iframe) as if it was a local object. Just use await
whenever the remote value is involed.
$ npm install --save comlinkjs
Comlink allows you to expose an arbitrary JavaScript value (objects, classes,
functions, etc) to the endpoint of an communications channel. Anything that
works with postMessage can be used as a communication channel. On the other
end of that channel you can use Comlink to synthesize an ES6 proxy. Every action
performed on that proxy object will be serialized using a simple (and naïve) RPC
protocol and be applied to the exposed value on the other side.
Size: ~2.5k, ~1.1k gzip’d.
<-- index.html -->
<!doctype html>
<script src="../../dist/comlink.global.js"></script>
<script>
const worker = new Worker('worker.js');
// WebWorkers use `postMessage` and therefore work with Comlink.
const api = Comlink.proxy(worker);
async function init() {
// Note the usage of `await`:
const app = await new api.App();
alert(`Counter: ${await app.count}`);
await app.inc();
alert(`Counter: ${await app.count}`);
};
init();
</script>// worker.js
importScripts('../dist/comlink.global.js');
class App {
constructor() {
this._counter = 0;
}
get count() {
return this._counter;
}
inc() {
this._counter++;
}
}
Comlink.expose({App}, self);The Comlink module is provided in 3 different formats:
-
“es6”: This package uses the native ES6 module format. Due to some necessary hackery, the module exports a
Comlinkobject. Import it as follows:import {Comlink} from '../dist/comlink.es6.js'; // ...
-
“global”: This package adds a
Comlinknamespace onself. Useful for workers or projects without a module loader. -
“umd”: This package uses UMD so it is compatible with AMD, CommonJS and requireJS.
These packages can be mixed and matched. A worker using global can work
with a window using es6. For the sake of network conservation, I do recommend
sticking to one format, though.
The Comlink module exports 3 functions:
proxy creates an ES6 proxy and sends all operations through the channel behind
endpoint. The other end of the channel should be passed to expose.
expose listens for RPC messages on endpoint and applies the operations to
rootObj. The return value will be structurally cloned and sent back. Values
that implement the Transferable interface will be transferred.
If structurally cloning a return value is undesired, wrapping the value in a
proxyValue call will cause expose to send back a
MessagePort instead of the actual value. The MessagePort will
be hooked up to a new proxy on the other end.
If a window is to be used as an endpoint, the value must be wrapped by
windowEndpoint so that messages will be dispatched correctly.
const ifr = document.querySelector('iframe');
Comlink.proxy(Comlink.windowEndpoint(ifr.contentWindow));License Apache-2.0
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