message: Small pretty refactor for knockout progress buttons
diff: import * as ko from "knockout";
  import { SurveyModel } from "../../../survey";
  import { SurveyProgressButtonsModel } from '../../../surveyProgressButtons';
  -var template = require("html-loader?interpolate!val-loader!./buttons.html");
  +const template: any = require("html-loader?interpolate!val-loader!./buttons.html");
  export class ProgressButtonsViewModel {
  private progressButtonsModel: SurveyProgressButtonsModel;
  private scrollButtonCssKo: any = undefined;
  private hasScroller: any = ko.observable(false);
  private updateScroller: any = undefined;
  - constructor (private model: SurveyModel, private element: any) {
  + constructor (private model: SurveyModel, element: any) {
  this.progressButtonsModel = new SurveyProgressButtonsModel(model);
  this.updateScroller = setInterval(() => {
  - let listContainerElement: HTMLElement = this.element.querySelector(
  + let listContainerElement: HTMLElement = element.querySelector(
  "." + model.css.progressButtonsListContainer);
  if (!!listContainerElement) {
  this.hasScroller(listContainerElement.scrollWidth > listContainerElement.offsetWidth);
  