How to assign a value to a variable in SASS depending on the screen size?

Question

Sass

Suppose there is a variable $a. How can I make it so that if media max-device-width > 1000 then $a = 1000px otherwise $a = 800px.

Answer 1

No way, sass is not processed in the browser, but compiled into css.
And this is how, for example, the width of the container is set in Bootstrap 4, depending on the breakpoints
. Open the source code on the github and study it.

Answer 2

It seems that variables are not needed here.
Just use media queries wisely.