Error Handler Class for Node js tutorial with Express

ErrorHandler.js

/**
 * Modified from the Connect project: https://github.com/senchalabs/connect/blob/master/lib/middleware/errorHandler.js
 *
 * Flexible error handler, providing (_optional_) stack traces and logging
 * and error message responses for requests accepting text, html, or json.
 *
 * Options:
 *
 *   - `showStack` respond with both the error message and stack trace. Defaults to `false`
 *   - `showMessage`, respond with the exception message only. Defaults to `false`
 *   - `dumpExceptions`, dump exceptions to stderr (without terminating the process). Defaults to `false`
 *   - `logErrors`, will dump a log entry and stack trace into the gievn file. Defaults to `false`
 *
 * Text:
 *   By default, and when _text/plain_ is accepted a simple stack trace
 *   or error message will be returned.
 *
 * JSON:
 *   When _application/json_ is accepted, connect will respond with
 *   an object in the form of `{ "error": error }`. 
 *
 * HTML:
 *   When accepted connect will output a nice html stack trace.
 *
 * @param {Object} options
 * @return {Function}
 * @api public
 */

var fs = require('fs');

exports = module.exports = function errorHandler(options){
	options = options || {};
	// defaults
	var showStack = options.showStack
		, showMessage = options.showMessage
		, dumpExceptions = options.dumpExceptions
		, logErrors = options.logErrors
		, logErrorsStream = false;
	
	if(options.logErrors)
		logErrorsStream = fs.createWriteStream(logErrors, {'flags': 'a', encoding: 'utf-8', mode: 0666});

	return function errorHandler(err, req, res, next){
	    res.statusCode = 500;

	    if(dumpExceptions) console.error(err.stack);

		if(logErrors){
			var now = new Date();
			logErrorsStream.write(now.toJSON() + ' - Error Happened: \n' + err.stack + "\n");
		}

		var accept = req.headers.accept || '';
	    if(showStack) {
			// html
			if (~accept.indexOf('html')) {
				res.render('error.jade', {
					  layout: false
					, stack: err.stack || ''
					, error: err.toString() 
					});
			// json
			} else if (~accept.indexOf('json')) {
				var json = JSON.stringify({ error: err });
				res.setHeader('Content-Type', 'application/json');
				res.end(json);
			// plain text
			} else {
				res.writeHead(500, { 'Content-Type': 'text/plain' });
				res.end(err.stack);
			}
	    }else{
			// public error page render
			// html
		  	if (~accept.indexOf('html')) {
				res.render('error.jade', {
						  layout: false
						});
			// json
			} else if (~accept.indexOf('json')) {
				var json = JSON.stringify({ error: "There was a server error generating the content." });
				res.setHeader('Content-Type', 'application/json');
				res.end(json);
			// plain text
			} else {
				res.writeHead(500, { 'Content-Type': 'text/plain' });
				res.end("500 - Server Error");
			}
	    }
	};
};