dropdown.js

function setPosition(el, ctrl) {
  var rect = el.getBoundingClientRect()
  if (rect.left < 0) {
    ctrl.position('left')
  } else {
    ctrl.position('right')
  }
}

function initSubEvents(el, ctrl) {
  setPosition(el, ctrl)
  window.addEventListener('resize', function() {
    setPosition(el, ctrl)
  })
}

m('sub', {
  config: function(el, isInitialized, context) {
    if (isInitialized) return
    initSubEvents(el, ctrl)
    context.onunload = function() {
      clearEvents()
    }
  },
  position: ctrl.position()
})