Solve your z-index: 999 problems: A set of zIndex defaults.
With npm do:
$ npm install app-levels --save-dev
or
$ yarn add app-levels
In Javascript
import appLevels from 'app-levels'
<div style={{ zIndex: appLevels.LEVEL_POPUP}}></div>
In SASS
import '../node_modules/app-levels/index.sass'
.my-popup {
z-index: $LEVEL_POPUP
}
LEVEL_SUPPORT_OVERLAY: 60
LEVEL_ALERT: 50
LEVEL_POPUP: 40
LEVEL_NAV_MOBILE: 30
LEVEL_NAV: 20
LEVEL_OVERLAYS: 10
LEVEL_BASE: 0
LEVEL_BACKGROUND: -10
MIT