nakree

import {NavLink} from 'react-router-dom';
<li>
  <NavLink to="/" activeClassName="active">
    <u>Главная</u>
  </NavLink>
</li>
<li>
  <NavLink to="/about" activeClassName="active">
    <u>О нас</u>
  </NavLink>
</li>

const str = 'abcde'

function reverseString(str) {
  let tempString = ''
  for(let j = str.length - 1; j >= 0; j--){
   	tempString += str[j]
  }
  return tempString
}

console.log('str:', str)
console.log('reverse:', reverseString(str))

const str = 'abcde'

function reverseString(str) {
 return str.split('').reverse().join('')
}

console.log('str:', str)
console.log('reverse:', reverseString(str))

npm init react-app my-app
npm run eject

const duration = '30';
const startTime = moment().format('DD-MM-YYYY') // 26-10-2018
const endTime = moment().add(duration, 'days').format('DD-MM-YYYY') // 26-11-2018

const duration = {
   years:  '1',
   months: '5',
   days: '30'
};
const startTime = moment().format('DD-MM-YYYY') // 26-10-2018
const endTime = moment().add(duration).format('DD-MM-YYYY') //  примерно 25-05-2020

class Container extends React.Component {
  state = {
   showModal: false
  }

  handleModal = () => {
    this.setState({showModal: !this.state.showModal});
  }
render() {
  return (
    <Fragment>
      { this.state.showModal && <MyModal handleModal={this.handleModal}/> }
      <button onClick={this.handleModal}> Show modal </button>
    </Fragment>
   )
}

var list = document.getElementsByClassName('list')[0];
var item = list.getElementsByClassName('item')[3];

let elem = document.querySelector('.element[data-attr=this-element]')

let [elem] = [...document.getElementsByClassName('element')]
.filter((item) => { return item.getAttribute('data-attr') === 'this-element' })

let [elem] = [...document.getElementsByClassName('element')]
.filter((item) => { return item.dataset.attr === 'this-element' })