isDateFormat
function isDateFormat(numberFormat): boolean;Whether a number format string formats its value as a date, matching what Excel treats as one.
True when the format carries a date component — a day or year token, as in yyyy-mm-dd or
d mmm. False for a plain numeric format, and false for a time-only format such as hh:mm:
numfmt’s own isDateFormat counts those as date formats, this one does not.
Parameters
Section titled “Parameters”numberFormat
Section titled “numberFormat”string | undefined
Returns
Section titled “Returns”boolean