npm init

npm install --save-dev postcss postcss-filter-mq

var postcss = require("postcss"),
    filtermq = require("postcss-filter-mq"),
    fs = require('fs');

fs.readFile('input.min.css', function(err, css) {
    postcss([ filtermq({invert: true, keepBaseRules: true}) ])
        .process(css, { from: "input.min.css", to: "output.min.css" })
        .then(function (result) {
            fs.writeFileSync("output.min.css", result.css);
            if ( result.map ) fs.writeFileSync("output.min.css.map", result.map);
        });
});