logcalltracer

A minimalistic library that shows the caller's location in log messages, with an optional timestamp, log level.

Usage

You can use the following methods, the same way you would use console.log, .warn, and .error methods:

• logInfo
• logWarn
• logError

The default output is the caller's location, then the values of the parameters. Example:

// Import module
const logger = require("logcalltracer");

logger.logInfo("Hello world!")

shows the following output:

/myApp/start.js:4: Hello world!

Supported environments

• Node.js >= 12.22.1
• Deno >= 1.12.0

This package is intended to be used in server applications based on Node.js and Deno. Browsers are not supported, but logcalltracer seems to work with:

• Brave 1.27.108 Chromium: 92.0.4515.107 (Official Build) (64-bit)
• Chrome 91.0.4472.164 (Official Build) (64-bit)
• Edge 92.0.902.55 (Official build) (64-bit)
• FireFox 90.0.2 (64-bit)

Customizing output

The library can be configured to provide additional information, such as timestamp, log level, coloring, and so on. Use the following properties on the options object:

timeStampFormatter : Function

A method to get a formatted timestamp. The default value is undefined, so log output has no timestamp. You can use the built-in Date object or any 3rd party library to provide a method that returns your preferred timestamp.

Example:

// Import module
const logger = require("logcalltracer");

logger.options.timeStampFormatter = () => new Date().toISOString();

logger.logInfo("Hello world!")

shows the following output:

2021-06-04T11:57:43.175Z  /myApp/start.js:4: Hello world!

showLogLevel: boolean

When set to true, the output displays the log level.

inspectOptions: object

This library uses util.inspect to format arguments. You can change the default formatting behavior using the inspectOptions: https://nodejs.org/dist/latest-v16.x/docs/api/util.html#util_util_inspect_object_options

For a development environment, I suggest the following to start with:

const logger = require("logcalltracer");
logger.options.inspectOptions = {compact: false, depth: Infinity};

logInfoFn: Function, and logWarnFn, logErrorFn

By default, the methods are mapped to the console's logging methods:

Method	Calls
logInfo	console.log(timestamp?, info?, callerLocation, ...arguments)
logWarn	console.warn(timestamp?, warn?, callerLocation, ...arguments)
logError	console.error(timestamp?, err?, callerLocation, ...arguments)

You can plug in your own, or an external logging library's logger methods. Example:

const logger = require("logcalltracer")
const util = require("util")
const fs = require("fs");

logger.options.logInfoFn = function(timestamp, logLevel, callerLocation, ...rest) {
    console.log("My custom logging method");
    fs.appendFile(
        "test.log",
        `${timestamp} ${logLevel} ${callerLocation} ${util.formatWithOptions.apply(null, [logger.options.inspectOptions, ...rest])}\n`,
        "utf8",
        err => {});
}

logger.options.timeStampFormatter = () => new Date().toISOString();
// logger.options.showLogLevel is not set, so it won't be passed to the logInfoFn method.
logger.logInfo("Application starting..", { a: 42, b: { c: 'Hi!'}});

will create a file with the following content:

2021-06-04T12:26:09.455Z  /myApp/start.js:16: Application starting.. { a: 42, b: { c: 'Hi!' } }

logLevelColored: get/set(boolean)

By default, no coloring is performed on the output. When both showLogLevel and logLevelColored are set to true, the log level is colored as follows:

Method	Color
logInfo	None
logWarn	Yellow
logError	Red

An example with options

// Import module
const logger = require("logcalltracer");

// Customize the behavior if you want to.
if (process.env.NODE_ENV === "production") {
  logger.options.timeStampFormatter = () => new Date().toISOString();
  logger.options.showLogLevel = true;
  logger.options.inspectOptions = {compact: false};
} else {
  logger.options.timeStampFormatter = () => new Date().toLocaleTimeString();
  logger.options.inspectOptions = {compact: false, depth: Infinity};
  logger.options.logLevelColored = true;
  logger.options.showLogLevel = true;
}

logger.logInfo("Application starting..", { a: 42, b: { c: 'Hi!'}});

shows the following output:

1:42:13 PM INFO  c:\myApp\start.js:16: Application starting.. {
  a: 42,
  b: {
    c: 'Hi!'
  }
}

License

MIT