How to execute javascript after DOM is loaded in cycle.js

How can I execute javascript after the DOM is loaded in cycle.js? I can't put it in my main() because the DOM is not loaded at that point. For context, I'm basically trying to initialize a fancy autocomplete which requires the target DOM element to exist, please feel free to give pointers if my approach is wrong.

I tried this:

sources.DOM.select(':root')
  .observable.take(1)
  .subscribe((element) => initAutoCompl())

...but select was returning null, I also tried selecting against other elements as well.

One way (using CycleJS with xstream) to execute JS code once after the DOM is ready is to run a (otherwise) non-operative observable. To do that select ':root' then assign a non-existent event, and initiate the stream with startWith. Once the stream is initiated run a map that executes your setup function. To subscribe to the observable send it to a non-operative driver:

function main (sources) {

  // Initiate observable, run setup function
  const noop$ = sources.DOM.select(':root').events('noop')
    .startWith(1).map(noop => runSetup())

...

  return {
    DOM: vdom$,
    noop: noop$
  }
}

...

Cycle.run(main, {
  DOM: makeDOMDriver('#app'),

  // non-operative driver
  noop: noop$ => { noop$.addListener(
    {next: noop => {}, error: ()=>{}, complete: ()=>{}}
  ) }
})

Codepen.io Run Setup example

---

Another way is to run your setup script in a driver and trigger it with an of observable.

function main (sources) {

  // trigger observable
  const setup$ = xs.of(1)

...

  return {
    DOM: vdom$,
    setup: setup$
  }
}

Cycle.run(main, {
  DOM: makeDOMDriver('#app'),

  // setup driver
  setup: setup$ => { setup$.addListener({next: setup => {
    // setup code goes here
    console.log('run setup: ', document.querySelector('#app').children.length)
  }, error: ()=>{}, complete: ()=>{}}) }
})

Codepen.io Setup Driver example.

---

If user input is needed before creating the DOM element:

function main (sources) {

  const click$ = sources.DOM.select('div#clickme').events('click')
  const vdom$ = click$
    .mapTo(div('#newDomElement',"I'm new."))
    .startWith(div('#clickme','Click me.'))

  return {
    DOM: vdom$,
    setup: click$
  }
}

Cycle.run(main, {
  DOM: makeDOMDriver('#app'),
  setup: setup$ => { setup$.addListener({next: setup => {
    // setup code goes here
    initAutoComplDummy()
  }, error: ()=>{}, complete: ()=>{}}) }
})

Codepen.io Setup Driver After User Input example