postcss-ie11-supports/lib/index.js

PostCSS plugin adding "@supports not" support for IE 11

import postcss from 'postcss';

import * as constants from './constants.js';

export const plugin = postcss.plugin('postcss-ie11-supports', ({
    ieSelector = constants.ieSelector,
} = {}) => root => {
    root.walkAtRules('supports', atRule => {
        if (/^not\b/.test(atRule.params)) {
            const newRules = atRule.clone();
            newRules.walkRules(rule => {
                rule.selector = `${ ieSelector }, ${ rule.selector }`;
            });
            atRule.after(newRules.nodes);
        }
    });
});