Simple mutation observer on attributes.

MutationObserverAttributes.ts

/**
 * Mutation observer is not a big library. Rather it's a simple way to observe:
 * 1. New attributes on nodes.
 * 2. Added / removed node to document.
 * 3. Changes to "contenteditable" text elements.
 */

const observer = new MutationObserver((mutationsList, observer) => {
  for (let mutation of mutationsList) {
    if (mutation.type === 'attributes') {
      console.log(mutation.attributeName)
    }
  }
})

observer.observe(document, {
  subtree: true,
  attributes: true,
  attributeFilter: ['data-authpack']
})

setTimeout(() => {
  const node = document.createElement('div')
  const parent = document.querySelectorAll('[data-authpack]')[0]
  if (parent) parent.appendChild(node)
  node.dataset.authpack = 'hello'
  setTimeout(() => observer.disconnect())
}, 1000)