How to implement a graph with gradient (background) + forecast line?

Question

css

Hello! How to implement a graph with such a gradient in the background? Also need a forecast line (dashed)

Answer 1

Masks.

Answer 2

Gradient line jsfiddle.net/9bMPD
The idea is to make a gradient that can be used as a fill for a polygon or a line.
The dashed line style is set for the entire context at once with
After use, it must be reset.