5-java-script-practices-that-will-help-your-teammates-sleep-at-night_9.js

// elements.js
function getIframe(container = document.body) {
  return new Promise((resolve, reject) => {
    const attributes = { src: 'http://www.google.com/abc.png' }
    const elem = document.createElement('iframe')

    // Assuming "attributes" also includes the "src"
    Object.entries(attributes).forEach(([attr, value]) => {
      elem.setAttribute(attr, value)
    })

    elem.addEventListener('load', function (evt) {
      resolve(elem)
    })

    elem.addEventListener('error', reject)
  })
}

// app.js
import { getIframe } from '../elements'

async function initContainer({ children, tagName = 'div' } = {}) {
  const container = document.createElement(tagName)
  if (children) {
    container.appendChild(await children(container))
  }
  return container
}

async function startApp() {
  await initContainer({ children: getIframe })
}