content: import React, { Component } from 'react';
  import PropTypes from 'prop-types';
  
  class Ruler extends Component {
    render() {
      const { startTime, endTime } = this.props;
      let hours = [];
      for (let i = Math.floor(startTime); i <= Math.floor(endTime); i++) {
        let time;
        if (i > 12) {
          time = i - 12 + ':00 pm';
        } else {
          time = i + ':00 am';
        }
        hours.push(time);
      }
      let ticks = hours.map((hour) => (
        <li className="ruler_tick" key={hour}>
          {hour}
        </li>
      ));
  
      return <ul className="schedule_ruler">{ticks}</ul>;
    }
  }
  
  Ruler.propTypes = {
    startTime: PropTypes.number,
    endTime: PropTypes.number,
  };
  
  export { Ruler };
  