text: dayjs(new Date()).isValid();
  // output => true
  
  dayjs("2019–10–04").isBefore("2019–10–06");
  // output => true
  
  dayjs("2019–10–04").isSame("2019–10–06");
  // output => false
  dayjs("2019–10–04").isSame("2019–10–04");
  // output => true
  dayjs("2019–10–04").isSame("2019–10–06", "month");
  // output => true
  
  dayjs("2019–10–06").isAfter("2019–10–04");
  // output => true
  
  /*
  import isBetween from 'dayjs/plugin/isBetween';
  dayjs.extend(isBetween);
  */
  // dayjs requires isBetween plugin
  dayjs("2019–10–05").isBetween("2010–10–04", "2010–10–06");
  // output => true
  
  /*
  import isLeapYear from 'dayjs/plugin/isLeapYear';
  dayjs.extend(isLeapYear);
  */
  // dayjs requires isLeapYear plugin
  dayjs("2020–01–01").isLeapYear();
  // output => true
  