filter_module.js

var fs = require('fs');

module.exports = function(searchPath, searchExtension, callback)
{
	fs.readdir(searchPath, function(err, list)
	{
		if (err)
		{
			return callback(err);
		}
		
		var filteredList = new Array();
	
		for (var i = 0; i < list.length; i++)
		{
			var name = list[i];
	
			var startIndex = name.length - searchExtension.length;
			var endIndex = name.length;
			var extension = name.substring(startIndex, endIndex);
	
			if (extension == searchExtension)
				filteredList.push(name);
		}
	
		callback(null, filteredList);
	});
};

filter_test.js

var searchPath = process.argv[2];
var searchExtension = "." + process.argv[3];

var mymodule = require('./filter_module.js');

mymodule(searchPath, searchExtension, function(err, list)
{
	if (err)
	{
		return console.error("There was an error:", err);
	}
	
	list.forEach(function (file)
	{
		console.log(file);
	});
});