class MenuExample extends React.Component {
  constructor(props) {
    super(props);
    this.state = {f:0};
}

 clicke(fi) {
  this.setState({f:fi});
 }

 render() {
   const self = this;
   return (
     <ul>
       {
         this.props.items.map(
           (m,index) => {
             let style = '';
             if (self.state.focused == index) {
               style = 'focused';
             }
             return <li className={style} onClick={alert(m)}>{m}</li>
           }
         )
      }
  </ul>

  );
 }
}



ReactDOM.render(
   <MenuExample items={['MAIN','BLOG','ABOUT','CONTACT US']} />,
   document.getElementById("root")
);