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

? this.$refs.helpertextEl.foundation
          : void 0,

        leadingIcon: this.$refs.leadingIconEl
          ? this.$refs.leadingIconEl.foundation
          : undefined,
      },
    );

    if (this.menu_) {
      this.menu_.listen(
        MDCMenuSurfaceFoundation.strings.CLOSED_EVENT,
        this.handleMenuClosed,
      );
      this.menu_.listen(
        MDCMenuSurfaceFoundation.strings.OPENED_EVENT,
        this.handleMenuOpened,
      );
      this.menu_.listen(
        MDCMenuFoundation.strings.SELECTED_EVENT,
        this.handleMenuItemAction,
      );
    }

    this.foundation.init();
    // this.foundation.handleChange(false);

    // initial sync with DOM
    this.refreshIndex();
    // this.slotObserver = new MutationObserver(() => this.refreshIndex());
    // this.slotObserver.observe(this.$refs.native_control, {
    //   childList: true,

beforeDestroy() {
    // this.slotObserver.disconnect();
    if (this.menu_) {
      this.menu_.unlisten(
        MDCMenuSurfaceFoundation.strings.SELECTED_EVENT,
        this.handleMenuItemAction,
      );

      this.menu_.unlisten(
        MDCMenuSurfaceFoundation.strings.OPENED_EVENT,
        this.handleMenuOpened,
      );

      this.menu_.unlisten(
        MDCMenuSurfaceFoundation.strings.CLOSED_EVENT,
        this.handleMenuClosed,
      );
    }

    const foundation = this.foundation;
    this.foundation = null;