index.js

/*
 *  configurations
 *
 * {
 *		"log": {
 *			"type": "stdout" or "file",
 *			"color": true/false,
 *			"level": {
 *				"verbose": { "enabled": true/false, "path": "file path (required only if type is file)" },
 *				"debug": { "enabled": true/false, "path": "file path (required only if type is file)" },
 *				"info": { "enabled": true/false, "path": "file path (required only if type is file)" },
 *				"warning": { "enabled": true/false, "path": "file path (required only if type is file)" },
 *				"error": { "enabled": true/false, "path": "file path (required only if type is file)" },
 *				"fatal": { "enabled": true/false, "path": "file path (required only if type is file)" }
 *			}
 *		}
 * }
 *
 * */
var config = null;
var prefix = '';

var fs = require('fs');

var today = new Date();
var ymd = '.' + today.getFullYear() + '.' + (today.getMonth() + 1) + '.' + today.getDate();

module.exports.readConfig = function (configIn) {
	if (!configIn || !configIn.type) {
		throw new Error('invalid configurations:\n' + JSON.stringify(configIn, null, 4));
	}
	config = configIn;
	return true;
};

module.exports.setPrefix = function (prefixIn) {
	prefix = prefixIn;
};

module.exports.create = function (name) {
	return new Log(prefix, name);
};

function Log(prefix, name) {
	this._name = (prefix ? '(' + prefix + ')' : '') + '[' + name + ']';
}

Log.prototype.verbose = function () {
	var name = 'verbose';
	var msg = createMsg(this._name, name, arguments);
	print(name, msg);
};

Log.prototype.debug = function () {
	var name = 'debug';
	var msg = createMsg(this._name, name, arguments);
	print(name, msg);
};

Log.prototype.info = function () {
	var name = 'info';
	var msg = createMsg(this._name, name, arguments);
	print(name, msg);
};

Log.prototype.warning = function () {
	var name = 'warning';
	var msg = createMsg(this._name, name, arguments);
	print(name, msg);
};

Log.prototype.error = function () {
	var name = 'error';
	var msg = createMsg(this._name, name, arguments);
	print(name, msg);
};

Log.prototype.fatal = function () {
	var name = 'fatal';
	var msg = createMsg(this._name, name, arguments);
	print(name, msg);
};

function isEnabled(name) {
	if (config && config.level && config.level[name] && config.level[name].enabled) {
		return true;
	}
	return false;
}

function createMsg(logName, name, args) {
	var date = new Date();
	var ymd = date.getFullYear() + '/' + pad(date.getMonth() + 1, 2) + '/' + pad(date.getDate(), 2);
	var his = pad(date.getHours(), 2) + ':' + pad(date.getMinutes(), 2) + ':' + pad(date.getSeconds(), 2) + ':' + pad(date.getMilliseconds(), 3); 
	var timestamp = ymd + ' ' + his;
	var space = '';
	for (var i = 0, len = timestamp.length; i < len; i++) {
		space += ' ';
	}
	var msg = [color(name, '[' + timestamp + '] <' + name + '> ' + logName)];
	for (var key in args) {
		msg.push(color(name, args[key], space));
	}
	return msg;
}

function pad(n, digit) {
	n = n.toString();
	var len = n.length;
	if (len < digit) {
		var diff = digit - len;
		var padding = '';
		while (diff) {
			padding += '0';
			diff--;
		}
		n = padding + n;
	}
	return n;
}

function print(name, msg) {
	if (!isEnabled(name)) {
		
		if (!config || !config[name] || config[name].enabled === undefined) {
			// no configurations
			console.log.apply(console, msg);
		}

		return;
	}
	if (!config.type || config.type === 'stdout') {
		console.log.apply(console, msg);
	} else if (config.level && config.level[name] && config.level[name].path) {
		// write to a file
		var path = config.level[name].path + name + ymd + '.log';
		fs.appendFile(path, msg.join(' ') + '\n', function (error) {
			if (error) {
				throw new Error('failed to write a log to a file: ' + error);
			}
		});
	}
}

function color(name, msgItem) {
	var res = '';
	if (typeof msgItem === 'object') {
		if (msgItem instanceof Error) {
			msgItem = msgItem.message + '\n<stack trace>\n' + msgItem.stack;
		} else {
			msgItem = '\n' + JSON.stringify(msgItem, null, 4);
		}
	}
	if (!config || !config.color) {
		// no colors used
		return msgItem;
	}
	// log with colors
	switch (name) {
		case 'verbose':
			res = '\033[0;37m' + msgItem + '\033[0m';
			break;
		case 'debug':
			res = '\033[1;34m' + msgItem + '\033[0m';
			break;
		case 'info':
			res = '\033[0;32m' + msgItem + '\033[0m';
			break;
		case 'warning':
			res = '\033[1;35m' + msgItem + '\033[0m';
			break;
		case 'error':
			res = '\033[1;31m' + msgItem + '\033[0m';
			break;
		case 'fatal':
			res = '\033[1;37m\033[41m' + msgItem + '\033[0m';
			break;
		default:
			res = msgItem;
			break;
	}
	return res;
}