video-ad-sdk/src/adUnit/helpers/dom/__tests__/once.spec.ts

VAST/VPAID SDK that allows video ads to be played on top of any player

import {once} from '../once'

test('once must exec the listener once when the event occurs on the passed element', () => {
  const element = document.createElement('div')
  const listener = jest.fn()
  const eventName = 'test'

  once(element, eventName, listener)

  expect(listener).not.toHaveBeenCalled()

  element.dispatchEvent(new Event(eventName))

  expect(listener).toHaveBeenCalledTimes(1)

  element.dispatchEvent(new Event(eventName))

  expect(listener).toHaveBeenCalledTimes(1)
})

test('once must call the listener with all the args', () => {
  const element = document.createElement('div')
  const listener = jest.fn()
  const eventName = 'test'
  const event = new Event(eventName)

  once(element, eventName, listener)

  element.dispatchEvent(event)

  expect(listener).toHaveBeenCalledTimes(1)
  expect(listener).toHaveBeenCalledWith(event)
})

test('once must return a remove function', () => {
  const element = document.createElement('div')
  const listener = jest.fn()
  const eventName = 'test'

  const disconnect = once(element, eventName, listener)

  disconnect()

  element.dispatchEvent(new Event(eventName))
  element.dispatchEvent(new Event(eventName))

  expect(listener).toHaveBeenCalledTimes(0)
})