Weekday
WeekDay 增加了 .weekday() API 来获取或设置当前语言的星期。
var weekday = require("dayjs/plugin/weekday");
// import weekday from 'dayjs/plugin/weekday' // ES 2015
dayjs.extend(weekday);
// when Sunday is the first day of the week
dayjs().weekday(-7); // last Sunday
dayjs().weekday(7); // next Sunday
// when Monday is the first day of the week
dayjs().weekday(-7); // last Monday
dayjs().weekday(7); // next Monday