Emitter

Class that implements the event emitter pattern. Allows you to specify the context (this value) and to remove listeners based on that context.

import { Emitter } from 'oblik/utils/emitter'

let emitter = new Emitter()
let listener = function (value, value2) {
    console.log('context', this)
    console.log('values', value, value2)
}

emitter.on(
    'test',   // event name
    listener, // callback
    'foo'     // context
)

// Emit a "test" event with the values "bar" and "baz"
emitter.emit('test', 'bar', 'baz')

// Remove the specified listener from the "test" event.
emitter.off('test', listener)

// Remove all "test" listeners where the context is "foo".
emitter.off('test', null, 'foo')

// Remove all listeners where the context is "foo".
emitter.purge('foo')

context "foo"
values "bar" "baz"

If you're using TypeScript, you can specify event types as well:

type Events = {
    foo: (text: string) => void
}

let emitter = new Emitter<Events>()
emitter.emit('foo', 42) // Argument of type '42' is not assignable
                        // to parameter of type 'string'. ts(2345)

# Promises

You can also wait for an event with a Promise. It's just a promisified once() call:

emitter.promise('test').then(() => {
    // "test" event resolved
})