Get last fetched data when key is null

[hellow554]

I'm polling some numbers from a webpage, but at the same you can also edit that number that I'm polling (think of it like getting a value for a variable but be able to set it).

Therefore I have either a <div> that contains the value or when you toggle a button you have a <input> field.

When I click that button I don't want to fetch that data anymore (because I'm about to edit it), but I want to last value that has been fetched as an initial value for my input field.

But when I set the key to null via conditional fetching the data will be reset to null as well.

Is there a way to get the last fetched data (prefereable without storing it in the mean time)?