working with the HTML textbox onchange event with JavaScript

I saw this example
https://www.w3schools.com/tags/tryit.asp?filename=tryhtml5_ev_onchange2

When you run it, it looks like this. So the textbox has the value Hello.


Now I type the word World in the textbox and click outside the textbox which fires the onchange event like this.



Is there a way to store the existing value of the textbox in a hidden field and also store the new text i typed in the textbox in a hidden field also, but separately.

So when I run the above example and then type World.

I want to store the existing value which is "Hello" in a hidden field called HiddenField1
and the new text that I typed in the textbox which is "World" in a hidden field called HiddenField2

What's the best way to do that?