Line fill effect on scroll?

Question

JavaScript

It is necessary to make an animation as in the example, but my eye starts to twitch when I see how everything works there is scary ...
Are there any options for how this can be done easier? Yes, and adaptive ... although in the mobile version I think you can just turn it off.

Answer 1

www.w3schools.com/howto/howto_js_scrolldrawing.asp
scrollmagic.io/examples/advanced/svg_drawing.html
codepen.io/paintbycode/pen/JDbcF

Answer 2

It is very easy!
We hang it on window.onscrolla function in which we calculate the offset of an invisible element, etc.