Unreliable method to detect date in _isDate

[peter-walter]

table-sortable/src/utils.js

Line 17 in 75662e5

if (_isNumber(d.getDate())) {

In Chome 88:
_isDate('31') === false
_isDate('32') === true
_isDate('999') === true
_isDate('1000') === true

In Firefox 84
_isDate('31') === false
_isDate('32') === false
_isDate('999') === false
_isDate('1000') === true