How to use the @material/menu-surface/foundation.MDCMenuSurfaceFoundation.strings function in @material/menu-surface

MDCMenu.prototype.initialSyncWithDOM = function () {
        var _this = this;
        this.menuSurface_ = this.menuSurfaceFactory_(this.root_);
        var list = this.root_.querySelector(strings.LIST_SELECTOR);
        if (list) {
            this.list_ = this.listFactory_(list);
            this.list_.wrapFocus = true;
        }
        else {
            this.list_ = null;
        }
        this.handleKeydown_ = function (evt) { return _this.foundation_.handleKeydown(evt); };
        this.handleItemAction_ = function (evt) { return _this.foundation_.handleItemAction(_this.items[evt.detail.index]); };
        this.handleMenuSurfaceOpened_ = function () { return _this.foundation_.handleMenuSurfaceOpened(); };
        this.menuSurface_.listen(MDCMenuSurfaceFoundation.strings.OPENED_EVENT, this.handleMenuSurfaceOpened_);
        this.listen('keydown', this.handleKeydown_);
        this.listen(MDCListFoundation.strings.ACTION_EVENT, this.handleItemAction_);
    };
    MDCMenu.prototype.destroy = function () {

initialSyncWithDOM() {
    this.afterOpenedCallback_ = () => this.handleAfterOpened_();
    this.handleKeydown_ = (evt) => this.foundation_.handleKeydown(evt);
    this.handleClick_ = (evt) => this.foundation_.handleClick(evt);

    this.menuSurface_.listen(MDCMenuSurfaceFoundation.strings.OPENED_EVENT, this.afterOpenedCallback_);
    this.listen('keydown', this.handleKeydown_);
    this.listen('click', this.handleClick_);
  }

open_ = (): void => {
    if (this.props.open) {
      if (!this.menuSurfaceElement.current) return;
      const focusableElements = this.menuSurfaceElement.current.querySelectorAll(
        MDCMenuSurfaceFoundation.strings.FOCUSABLE_ELEMENTS
      );
      this.firstFocusableElement =
        focusableElements.length > 0 ? focusableElements[0] as HTMLElement : null;
      this.lastFocusableElement =
        focusableElements.length > 0
          ? focusableElements[focusableElements.length - 1] as HTMLElement
          : null;
      this.foundation.open();
    } else {
      this.foundation.close();
    }
  };