text: import React from 'react'
  import PropTypes from 'prop-types'
  
  export default class Elapse extends React.Component {
    componentDidMount () {
      this.interval = setInterval(this.props.plus, 1000)
    }
  
    componentWillUnmount () {
      clearInterval(this.interval)
    }
  
    render () {
      const { elapse } = this.props
      return (
        <h3>
          Seconds Elapsed: {elapse}
        </h3>
      )
    }
  }
  
  Elapse.propTypes = {
    elapse : PropTypes.number.isRequired,
    plus   : PropTypes.func.isRequired
  }
  