Parse urls from css file
npm install css-url-parser
var parseCssUrls = require('css-url-parser');
var css = '@import "a.css"; .image { background-image: url(images/img.png); }';
var cssUrls = parseCssUrls(css);
console.log(cssUrls); // [ 'a.css', 'images/img.png' ]
It ignores duplicated urls and base64 encoded resources. If no urls found empty array will be returned.