this version will run with npm start, but when attempting to run the built version behind nginx, it appears to have issues
PostCSS Focus Within 
PostCSS Focus Within lets you use the :focus-within pseudo-class in CSS,
following the Selectors Level 4 specification.
It is the companion to the focus-within polyfill.
.my-form-field:focus-within label {
background-color: yellow;
}
/* becomes */
.my-form-field[focus-within] label {
background-color: yellow;
}
.my-form-field:focus-within label {
background-color: yellow;
}
PostCSS Focus Within duplicates rules using the :focus-within pseudo-class
with a [focus-within] attribute selector, the same selector used by the
focus-within polyfill. This replacement selector can be changed using the
replaceWith option. Also, the preservation of the original :focus-within
rule can be disabled using the preserve option.
Usage
Add PostCSS Focus Within to your project:
npm install postcss-focus-within --save-dev
Use PostCSS Focus Within to process your CSS:
const postcssFocusWithin = require('postcss-focus-within');
postcssFocusWithin.process(YOUR_CSS /*, processOptions, pluginOptions */);
Or use it as a PostCSS plugin:
const postcss = require('postcss');
const postcssFocusWithin = require('postcss-focus-within');
postcss([
postcssFocusWithin(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);
PostCSS Focus Within runs in all Node environments, with special instructions for:
| Node | PostCSS CLI | Webpack | Create React App | Gulp | Grunt |
|---|
Options
preserve
The preserve option defines whether the original selector should remain. By
default, the original selector is preserved.
focusWithin({ preserve: false });
.my-form-field:focus-within label {
background-color: yellow;
}
/* becomes */
.my-form-field[focus-within] label {
background-color: yellow;
}
replaceWith
The replaceWith option defines the selector to replace :focus-within. By
default, the replacement selector is [focus-within].
focusWithin({ replaceWith: '.focus-within' });
.my-form-field:focus-within label {
background-color: yellow;
}
/* becomes */
.my-form-field.focus-within label {
background-color: yellow;
}
.my-form-field:focus-within label {
background-color: yellow;
}