The preserve option determines whether Custom Properties and properties using custom properties should be preserved in their original form. By default, both of these are preserved.
The importFrom option specifies sources where Custom Properties can be imported from, which might be CSS, JS, and JSON files, functions, and directly passed objects.
postcssCustomProperties({ importFrom:'path/to/file.css'// => :root { --color: red }});
Multiple sources can be passed into this option, and they will be parsed in the order they are received. JavaScript files, JSON files, functions, and objects will need to namespace Custom Properties using the customProperties or custom-properties key.
The exportTo option specifies destinations where Custom Properties can be exported to, which might be CSS, JS, and JSON files, functions, and directly passed objects.
Multiple destinations can be passed into this option, and they will be parsed in the order they are received. JavaScript files, JSON files, and objects will need to namespace Custom Properties using the customProperties or custom-properties key.