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Is Same or Before

This indicates whether the Day.js object is the same or before another supplied date-time.

This requires the IsSameOrBefore plugin to work

dayjs.extend(isSameOrBefore)
dayjs().isSameOrBefore(dayjs('2011-01-01')) // default milliseconds

If you want to limit the granularity to a unit other than milliseconds, pass it as the second parameter.

dayjs().isSameOrBefore('2011-01-01', 'year')

Units are case insensitive, and support plural and short forms.

List of all available units