fixUrls.js

/**
 * When source maps are enabled, `style-loader` uses a link element with a data-uri to
 * embed the css on the page. This breaks all relative urls because now they are relative to a
 * bundle instead of the current page.
 *
 * One solution is to only use full urls, but that may be impossible.
 *
 * Instead, this function "fixes" the relative urls to be absolute according to the current page location.
 *
 * A rudimentary test suite is located at `test/fixUrls.js` and can be run via the `npm test` command.
 *
 */

module.exports = function (css) {
  // get current location
  var location = typeof window !== "undefined" && window.location;
  
  if (!location) {
    throw new Error("fixUrls requires window.location");
  }

	// blank or null?
	if (!css || typeof css !== "string") {
	  return css;
  }

  var baseUrl = location.protocol + location.host;
  var currentDir = baseUrl + location.pathname.replace(/\/[^\/]*$/, "/");

	// convert each url(...)
	var fixedCss = css.replace(/url *\( *(.+?) *\)/g, function(fullMatch, origUrl) {
		// strip quotes (if they exist)
		var unquotedOrigUrl = origUrl
			.replace(/^"(.*)"$/, function(o, $1){ return $1; })
			.replace(/^'(.*)'$/, function(o, $1){ return $1; });

		// already a full url? no change
		if (/^(#|data:|http:\/\/|https:\/\/|file:\/\/\/)/i.test(unquotedOrigUrl)) {
		  return fullMatch;
    }

		// convert the url to a full url
		var newUrl;

		if (unquotedOrigUrl.indexOf("//") === 0) {
		  // add protocol
			newUrl = location.protocol + unquotedOrigUrl;
		} else if (unquotedOrigUrl.indexOf("/") === 0) {
			// path should be relative to the base url
			newUrl = baseUrl + unquotedOrigUrl; // already starts with '/'
		} else {
      // path should be relative to current directory
      newUrl = currentDir + unquotedOrigUrl.replace(/^\.\//, "") // Strip leading './'
		}

		// send back the fixed url(...)
		return "url(" + JSON.stringify(newUrl) + ")";
	});

	// send back the fixed css
	return fixedCss;
};