Possible issue with a MutationRecord object?

[Coop]

Hi, I'm having some issues getting an object property with dot-prop and I'm not sure why it's not working. Here's the code:

const dotProp = require('dot-prop')
const lodashGet = require('lodash.get')

const mainDiv = document.createElement('div')
mainDiv.setAttribute('id', 'main')

document.body.appendChild(mainDiv)

const mainElem = document.querySelector('#main')

const testerObj = {
  foo: 'bar'
}

console.log(dotProp.get(testerObj, 'foo'))
console.log(lodashGet(testerObj, 'foo'))

const observer = new MutationObserver(mutations => {
  mutations.forEach(mutation => {
    console.log(mutation)
    console.log(dotProp.get(mutation, 'addedNodes'))
    console.log(lodashGet(mutation, 'addedNodes'))
  })
})

observer.observe(
  mainElem,
  {
    childList: true,
    subtree: true,
    attributes: false,
    characterData: false,
    attributeOldValue: false,
    characterDataOldValue: false
  }
)

const newP = document.createElement('p')

mainElem.appendChild(newP)

I get the following output on the console:

bar
bar
MutationRecord { type: "childList", target: <div#main>, addedNodes: NodeList[1], removedNodes: NodeList[0], previousSibling: null, nextSibling: null, attributeName: null, attributeNamespace: null, oldValue: null }
undefined
NodeList [ <p> ]

If you want an easy way to try the code above, copy and paste it into https://esnextb.in/ and open the browser console to see the output.

Cheers.

[Steve Mao]

This requires the DOM tree. Is there an easier/minimal way to replicate the issue?

[Coop]

It looks like some earlier versions of jsdom had some MutationObserver support, so maybe you could try that: jsdom/jsdom#639

[Steve Mao]

What I meant is if there's a minimal way to replicate the issue? introducing MutationObserver makes it hard to demonstrate the issue

[Steve Mao]

I believe the issue is probably caused by MutationObserver. If you could prove the issue is caused by this module please comment :)