_renderNavBar() {
    const navBarStyle = {
      ...defaultStyle.navBarStyle,
      ...this.props.navBarStyle,
    };
    const monthLabelStyle = {
      ...defaultStyle.monthLabelStyle,
      ...this.props.monthLabelStyle,
    };

    return (
      <div
        style={ navBarStyle }
        { ...this.navBarProps }
      >
        { this._renderPrevMonthNav() }
        <span
          style={ monthLabelStyle }
          role="heading"
          /*
            This label has an id as suggested in http://www.w3.org/TR/wai-aria-practices/#datepicker
          */
          id={ `${this.state.year}-${this.state.month}` }
          { ...this.monthLabelProps }
        >
          { `${this.localeData.monthNames[this.state.month]} ${this.state.year}` }
        </span>
        { this._renderNextMonthNav() }
      </div>
    );
  }
Function will return jsx for rendering the nav bar for calendar.
Depending on following rules it will apply styles to prevMonthNav and nextMonthNav:
1. If disabled hide navs
2. If active apply activeStyles