with new_data, you can use .innerText/.textContent/.innerHTML, whichever works to your liking to get the content inside, and then, since it is a string, you can just use .split() if you wish to split it. If the content is a JSON object, you can use JSON.parse(the_string_here) to get a JSON object / Array from a string into the respective object.

If that doesn't help, could you share what the content of the html div looks like, so I could get a better understanding of what you're trying to accomplish?

You can simply take a storage variable and push the values from the div into it.

A simple example, which you probably still have to adjust.

const storage = []
document.getElementById('array').innerText = 'Hello';
storage.push( document.getElementById('array').innerText )


let newData = document.getElementById('array').innerText = document.getElementById('array').innerText + ' World';
storage.push(newData)
console.log(storage)

<div id="array"></div>