A script that recognizes Polymer element's URL and parses it to read location of assets like web workers to import during runtime.

polymer-import-location.js

var importLocation = '';
(function() {
  var url;
  if (window.currentImport && window.currentImport.URL) {
    url = window.currentImport.URL;
    if (window.currentImport._URL) {
      url = window.currentImport._URL;
    }
  } else if (window.currentImport._URL) {
    url = window.currentImport._URL;
  } else {
    url = window.location.href;
  }
  if (url === 'about:blank') {
    importLocation = '../';
    // in test cases for edge this will fail because it should be set to ../../
    // but right now I can't waste time to check how to check if this is the particular case.
  } else {
    var path = url.substr(url.indexOf('/', 8));
    path = path.substr(0, path.lastIndexOf('/') + 1);
    if (path.indexOf('/test') !== -1 || path.indexOf('/demo') !== -1) {
      path = path.substr(0, path.length - 1);
      path = path.substr(0, path.lastIndexOf('/') + 1);
    }
    importLocation = path;
  }
})();