A simple node.js web server

static_server.js

/*jslint onevar: true, undef: true, newcap: true, nomen: true, regexp: true, plusplus: true, bitwise: true, node: true, indent: 4, white: false */

/// Usage: node static_server.js PORT

var http = require("http"),
    url  = require("url"),
    path = require("path"),
    fs   = require("fs"),
    qs   = require("querystring"),
    port = process.argv[2] || 80,            /// Defaults to port 80
    dir  = process.argv[2] || process.cwd(); /// Defaults to current working directory

/// Start the server.
http.createServer(function (request, response)
{
    var filename,
        uri = qs.unescape(url.parse(request.url).pathname),;
    
    filename = path.join(dir, uri);
    
    /// Make sure the URI is valid and withing the current working directory.
    if (uri.substr(0,4) === "/../" || uri.substr(0, 1) !== "/" || path.relative(dir, filename).substr(0, 3) === "../") {
        response.writeHead(404, {"Content-Type": "text/plain"});
        response.write("404 Not Found\n");
        response.end();
        return;
    }
    
    fs.stat(filename, function (err, stats)
    {
        if (!err && stats.isDirectory()) {
            filename += "/index.html";
        }
        
        fs.exists(filename, function(exists) {
            if (!exists) {
                response.writeHead(404, {"Content-Type": "text/plain"});
                response.write("404 Not Found\n");
                response.end();
                return;
            }
            
            response.writeHead(200);
            
            /// Stream the data out to prevent massive buffers on large files.
            fs.createReadStream(filename, {"bufferSize": 4096}).pipe(response);
        });
    });
}).listen(parseInt(port, 10));

console.log("Static file server running at\n  => http://localhost:" + port + "/\nCTRL + C to shutdown");

Made it pass JSLint.

Made sure to parse the URI.

Stream data out to prevent massive buffers on large files.