stopwatch.js

import React, {Component, PropTypes} from 'react'
function _getTimeElapsedFromBeginDateTime (beginDateTime) {
  return Date.now() - beginDateTime
}
import moment from 'moment'
class StpWatch extends Component {
  constructor (props) {
    super(props)
    this.state = {timeElapsed: _getTimeElapsedFromBeginDateTime(this.props.beginDateTime)}
    this.updateTimeElapsed = this.updateTimeElapsed.bind(this)
  }
  componentDidMount () {
    this._timer = setInterval(() => this.updateTimeElapsed(), this.props.updateFrequency)
  }
  componentWillUnMount () {
    clearInterval(this._timer)
  }
  updateTimeElapsed () {
    this.setState({timeElapsed: _getTimeElapsedFromBeginDateTime(this.props.beginDateTime)})
  }
  render () {
    return <div>{this.state.timeElapsed} - {moment(this.props.beginDateTime).fromNow()}</div>
  }
}
StpWatch.defaultProps = {
  updateFrequency: 10 * 1000
}
StpWatch.propTypes = {
  beginDateTime: PropTypes.number.isRequired,
  updateFrequency: PropTypes.number
}
export default StpWatch