@environment-safe/event-emitter

A cross platform, source compatible emitter interface which uses a custom Emitter implementation (as opposed to integrating with native implementations as extended-emitter does). This allows implementations to vary and mutate without impacting downstream implementations.

event-emitter Usage

Usage should be (generally) as expected from the EventEmitter interface.

Browser Deps If you want to use from source in a browser, you need to add some dependenciess to your importmap you can do this programmatically with wing-kong or using testing with moka .moka in package.json or just manually in your HTML like:

<script type="importmap">{ "imports" :{
    "browser-or-node":"https://unpkg.com/[email protected]/src/index.js"
}}</script>

import

CommonJS

const { EventEmitter } = require('@environment-safe/event-emitter');
const emitter = new Emitter();

ES6 imports

import { EventEmitter } from '@environment-safe/event-emitter';
const emitter = new Emitter();

extended-emitter Usage

import

CommonJS

const { ExtendedEmitter } = require('@environment-safe/event-emitter');
const emitter = new Emitter();

ES6 imports

import { ExtendedEmitter } from '@environment-safe/event-emitter';
const emitter = new Emitter();

optional criteria

you can now use the DocumentQuery interface (supported by sift) to subscribe to specific events (in this context .once() means meeting the criteria, not just firing an event of that type).

emitter.on('my_object_event', {
    myObjectId : object.id
}, function(){
    //do stuff here
});

// or

emitter.once('my_object_event', {
    myObjectId : object.id,
    myObjectValue : {
        $gt : 20,
        $lt : 40
    }
}, function(){
    //do stuff here
});

.when()

and there's also the addition of a when function which can take ready-style functions, real promises or events, making it easy to delay or wait for a state, without resorting to chaining.

async

await emitter.when([$(document).ready, 'my-init-event', 'my-load-event']);

callbacks

emitter.when([$(document).ready, 'my-init-event', 'my-load-event'], function(){
    //do stuff
});

.onto()

Often you want an object to implement emitters, and while it's easy enough to wrap them, why not just have that done for you and avoid the boilerplate?

emitter.onto(MyClass.prototype);
emitter.onto(MyInstance);
emitter.onto(MyObject);

or in the constructor:

(new Emitter()).onto(this);

Testing

Run the es module tests to test the root modules

npm run import-test

to run the same test inside the browser:

npm run browser-test

to run the same test headless in chrome:

npm run headless-browser-test

to run the same test inside docker:

npm run container-test

Run the commonjs tests against the /dist commonjs source (generated with the build-commonjs target).

npm run require-test

Roadmap

Working toward exhaustive support of the EventEmitter interface.

Development

All work is done in the .mjs files and will be transpiled on commit to commonjs and tested.

If the above tests pass, then attempt a commit which will generate .d.ts files alongside the src files and commonjs classes in dist