How to use the @material/top-app-bar.MDCFixedTopAppBarFoundation function in @material/top-app-bar

if (!this._platform.isBrowser) { return 0; }

        return this._scrollTarget[this._scrollTarget === window ? 'pageYOffset' : 'scrollTop'];
      },
      getTotalActionItems: () => this.actions ? this.actions.length : 0
    };

    let foundation: MDCTopAppBarBaseFoundation;
    if (!this.elementRef) {
      return new MDCTopAppBarBaseFoundation(adapter);
    }

    if (this.short) {
      foundation = new MDCShortTopAppBarFoundation(adapter);
    } else if (this.fixed) {
      foundation = new MDCFixedTopAppBarFoundation(adapter);
    } else {
      foundation = new MDCTopAppBarFoundation(adapter);
    }
    return foundation;
  }

(this.scrollTarget as any)[
          'pageYOffset' in this.scrollTarget ? 'pageYOffset' : 'scrollTop'
        ],
      getTotalActionItems: () =>
        this.root.ref
          ? this.root.ref.querySelectorAll(
              MDCTopAppBarFoundation.strings.ACTION_ITEM_SELECTOR
            ).length
          : 0
    };

    let foundation;
    if (this.props.short) {
      foundation = new MDCShortTopAppBarFoundation(adapter);
    } else if (this.props.fixed) {
      foundation = new MDCFixedTopAppBarFoundation(adapter);
    } else {
      foundation = new MDCTopAppBarFoundation(adapter);
    }

    return foundation;
  }