js/util/once.js

export default function once (eeOrEventTarget, type) {
  return new Promise(resolve => {
    if ('once' in eeOrEventTarget) {
      eeOrEventTarget.once(type, evt => {
        resolve(evt)
      })
    } else if ('addEventListener' in eeOrEventTarget) {
      eeOrEventTarget.addEventListener(type, evt => {
        resolve(evt)
      }, { once: true })
    }
  })
}