Log js file name and function name

Question

I would like my node.js project to generate log files that are a bit similar to log4j format in that I would like each log line to commence with the file name and the js function name that the log request originated from.

e.g: If my js file is called aNiceFile.js and my js function is called doImportantStuff() and I invoke a log statement with something like:

log.info('About to start on the important stuff')

I would like my log file to look a bit like:

2018-03-14 06:33:26:619 INFO aNiceFile.js doImportantStuff() About to start on the important stuff.

I want to do a lot of logging, so I don't mind one off, upfront effort to set this up, but I am after minimal additional effort per file / function that I add to my code.

I am using Winston today, I am happy to switch to something else if that is necessary, with Winston this does not seem to be possible without some effort on my part: https://github.com/winstonjs/winston/issues/200

For completeness, I don't need the line numbers, but they would be nice to have too.

My current clumsy work around is to:

1) Start each file with this to get the current file name:

const sn = path.basename(__filename) // this script file name, used  for logging purposes

I am ok with this step, it is not onerous, a single identical line pasted at the top of each file, I can accept this.

2) Start each function with this to get the current function name:

const fn = '<I copy/paste the function name into this string constant :( >'

I don't like this step, I have to copy the function name into the string constant, and it could get out of sync later if I rename the function.

If I could turn this into the version below that would be better, not sure how to do that:

const fn = getCurrentFunctionName() 

3) I do each log statement like this:

log.info(`${sn}:${fn} Starting important stuff`)

I don't like this step because all my log statements start with this (${sn}:${fn}) noise.

As you can see this is primitive, but it does work. What should I really be doing here?

I am interested in performance so solutions that require the generation of an Error object to harvest a stack trace from are probably not acceptable.

Answer 1

Edit adding all stuff.

This is a basic example of filename, lines, columns and caller function. Maybe you need to adapt somethings. But this is the idea.

let log = {
	info: function info(message) {
		const callerInfo = getFileName(info.caller.name);
		console.log(
			new Date() +
				' ' +
				arguments.callee.name.toUpperCase() +
				' ' +
				callerInfo.filename +
				':' +
				callerInfo.line +
				':' +
				callerInfo.column +
				' ' +
				info.caller.name +
				'() ' +
				message
		);
	},
};

function getFileName(caller) {
  const STACK_FUNC_NAME = new RegExp(/at\s+((\S+)\s)?\((\S+):(\d+):(\d+)\)/);
	let err = new Error();
	
	Error.captureStackTrace(err);

	let stacks = err.stack.split('\n').slice(1);

	let callerInfo = null;
	for (let i = 0; i < stacks.length; i++) {
		callerInfo = STACK_FUNC_NAME.exec(stacks[i]);
    
		if (callerInfo[2] === caller) {
			return {
				filename: callerInfo[3],
				line: callerInfo[4],
				column: callerInfo[5],
			};
		}
	}

	return null;
}

function iWantToLog() {
	log.info('Testing my log');
}

iWantToLog();