docs: function getCurrentScript() {
          if ( currentlyAddingScript ) {
              return currentlyAddingScript;
          }
          else if (
              interactiveScript
              && interactiveScript.readyState === 'interactive'
          ) {
              return interactiveScript;
          }
          else {
              var scripts = document.getElementsByTagName( 'script' );
              var scriptLen = scripts.length;
              while ( scriptLen-- ) {
                  var script = scripts[ scriptLen ];
                  if ( script.readyState === 'interactive' ) {
                      interactiveScript = script;
                      return script;
                  }
              }
          }
      }