mine/node_modules/css-loader/dist/runtime/sourceMaps.js

"use strict";

module.exports = function (item) {
  var content = item[1];
  var cssMapping = item[3];
  if (!cssMapping) {
    return content;
  }
  if (typeof btoa === "function") {
    var base64 = btoa(unescape(encodeURIComponent(JSON.stringify(cssMapping))));
    var data = "sourceMappingURL=data:application/json;charset=utf-8;base64,".concat(base64);
    var sourceMapping = "/*# ".concat(data, " */");
    return [content].concat([sourceMapping]).join("\n");
  }
  return [content].join("\n");
};