Listening Once

Sometimes you might want to listen to a given event exactly once. Omnibus provides method .once to do exactly that.

You can use this method in two variants. When passing single argument, event name, the method will return a promise that will get resolved on the first event. This is an easy way to syncronise your events and listen to them in sequence.

import { Omnibus, args } from '@hypersphere/omnibus'

const bus = Omnibus.builder()
.register('log', args<string>())
.build()

// Pass bus to other async functions...

const result = await bus.once('log') // Log would need to be triggered from somewhere async

This method is especially useful when listening to other, external events, like clicks.

import { Omnibus } from '@hypersphere/omnibus'

const button = document.querySelector('button[.see-more]')

const bus = Omnibus.builder()
.from(button, 'click')
.build()

const clickEvent = await bus.once('click')

Another way to trigger event once is to pass a callback as a second parameter. Method in this form has the same signature like the .on method and you can use the unregister callback returned from .once call to unregister the callback before it is executed if needed.

import { Omnibus } from '@hypersphere/omnibus'

const button = document.querySelector('button[.see-more]')

const bus = Omnibus.builder()
.from(button, 'click')
.build()

const unregister = bus.once('click', (e) => {
    console.log('Button clicked', e)
})

setTimeout(unregister, 5000) // unregistering automatically after 5s.