Create custom slider for a custom visual plot

Hi guys,

i want to build a slider similar like in this picture here

Before i design the slider, i just want to read values dynamically from a simple textbox. I managed that without problems by creating a DOM-Element (input) with js

But as i try changing the value, it just stays static (it still returns the value 800)

Does anyone have i idea how to read the values from an textbox when i change the value on it?

		private createHelpLinkElement3(): Element {
            let linkElement = document.createElement("input");
			linkElement.setAttribute("value", "800");
            linkElement.setAttribute("class", "helpLink3");
            return linkElement;
        };

Here you can download my project