src/components/Header.js
/*  
   *  <Link> no longer has the activeClassName or activeStyle properties.
   *  In react-router v4 you have to use <NavLink>
   *  Refer to: https://stackoverflow.com/questions/41131450/active-link-with-react-router
   *            https://reacttraining.com/react-router/web/api/NavLink
   *  */
 no longer has the activeClassName or activeStyle properties.
no longer has the activeClassName or activeStyle properties .
render(){
    const links = headerLinks.map(({path, name}, key) =>
      key === 0
        ? this.renderFirstLinkElem(path, key)
        : <NavLink className={styles.link}
                   activeClassName={styles.active}
                   to={path}
                   exact
                   key={key}>
            {name}
          </NavLink>
    );
    return (
      <div className={styles.header}>
        <div className={styles.links}>
          {links}
        </div>
      </div>
    );
  }
render ( ) { const links = headerLinks . map ( ( { path , name } , key ) => key === 0 ? this . renderFirstLinkElem ( path , key ) : < NavLink className = { styles . link } activeClassName = { styles . active } to = { path } exact key = { key } > { name } < / NavLink > ) ; return ( < div className = { styles . header } > < div className = { styles . links } > { links } < / div > < / div > ) ; }
<Link> no longer has the activeClassName or activeStyle properties.
<Link > no longer has the activeClassName or activeStyle properties .