src/utils.js
/**
 Asserts whether the value is a valid date or timestamp.
 @protected
 @method assertIsDate
 @param {Date|Number} date The date or number value to check.
 @return {Boolean} whether the `date` is valid, will through if not.
 */
Asserts whether the value is a valid date or timestamp.
Asserts whether the value is a valid date or timestamp .
function assertIsDate(date, errMsg) {
    if (!isFinite(date)) {
        throw new TypeError(errMsg);
    }
    return true;
}
function assertIsDate ( date , errMsg ) { if ( ! isFinite ( date ) ) { throw new TypeError ( errMsg ) ; } return true ; }
Asserts whether the value is a valid date or timestamp.
Asserts whether the value is a valid date or timestamp .
// Determine if the `date` is valid by checking if it is finite, which is // the same way that `Intl.DateTimeFormat#format()` checks.