Pattern format and date docs

[thernstig]

According to https://github.com/log4js-node/log4js-node/blob/master/docs/layouts.md#pattern-format the pattern options are:

%d date, formatted - default is ISO8601, format options are: ISO8601, ISO8601_WITH_TZ_OFFSET, ABSOLUTE, DATE, or any string compatible with the date-format library. e.g. %d{DATE}, %d{yyyy/MM/dd-hh.mm.ss}

These names do not correspond to what is seen in the link specified, see https://www.npmjs.com/package/date-format#formatting-dates-as-strings

I assume this could be because log4js uses an older version? In any sense, it is confusing for users as one cannot check the npm site for the options, as they aren't completely identical.

[lamweili]

Perhaps this isn't clear, but there is a mapping from reserved log4js Strings in pattern options to date-format library options.

Reserved log4js String	dateFormat Constant (and String equivalent)	Output (local time)
"ISO8601"	dateFormat.ISO8601_FORMAT "yyyy-MM-ddThh:mm:ss.SSS"	2017-03-14T14:10:20.391
"ISO8601_WITH_TZ_OFFSET"	dateFormat.ISO8601_WITH_TZ_OFFSET_FORMAT "yyyy-MM-ddThh:mm:ss.SSSO"	2017-03-14T14:10:20.391+11:00
"ABSOLUTE"	dateFormat.ABSOLUTETIME_FORMAT "hh:mm:ss.SSS"	14:10:20.391
"DATE"	dateFormat.DATETIME_FORMAT "dd MM yyyy hh:mm:ss.SSS"	14 03 2017 14:10:20.391

The reserved Strings must match wholesomely.

log4js-node/lib/layouts.js

Lines 142 to 159 in 9fdbed5

	function formatAsDate(loggingEvent, specifier) {
	let format = dateFormat.ISO8601_FORMAT;
	if (specifier) {
	format = specifier;
	// Pick up special cases
	if (format === 'ISO8601') {
	format = dateFormat.ISO8601_FORMAT;
	} else if (format === 'ISO8601_WITH_TZ_OFFSET') {
	format = dateFormat.ISO8601_WITH_TZ_OFFSET_FORMAT;
	} else if (format === 'ABSOLUTE') {
	format = dateFormat.ABSOLUTETIME_FORMAT;
	} else if (format === 'DATE') {
	format = dateFormat.DATETIME_FORMAT;
	}
	}
	// Format the date
	return dateFormat.asString(format, loggingEvent.startTime);
	}

Perhaps the documentations need to be clearer.

[thernstig]

My intention was to check that if maybe ABSOLUTE should be renamed to ABSOLUTETIME and DATE to DATETIME to correspond 1-to-1 to what is in date-format. It is a minor thing really and possibly not worth it, since it is a breaking change. Or you could allow both e.g. ABSOLUTE and ABSOLUTETIME to map to dateFormat.ABSOLUTETIME_FORMAT. In any case it is not a big thing and maybe does not make sense, so it's possible this can be closed.

[lamweili]

That's a good suggestion to have both aliases.
One could be marked as deprecated (so it's non-breaking) for future releases in view of consistency.