Streaming combo handler

combo.js

var fs = require('fs'),
    Stream = require('stream'),
    util = require('util');

function ComboStream(files, opts) {
    Stream.call(this);
    opts = opts || {};

    if (!Array.isArray(files)) {
        throw new TypeError('First argument must be an Array');
    }
    if (Object(opts) !== opts) {
        throw new TypeError('Second argument must be an Object');
    }

    this._stack = files.concat();
    this._opts = opts;
    this._readNext();
}
util.inherits(ComboStream, Stream);
util._extend(ComboStream.prototype, {
    readable: true,
    writable: false,
    paused: false,
    pause: function () {
        this.paused = true;
        if (this._current) {
            this._current.pause();
        }
    },
    resume: function () {
        this.paused = false;
        if (this._current) {
            this._current.resume();
        }
    },
    setEncoding: function (encoding) {
        this._opts.encoding = encoding;
        if (this._current) {
            this._current.setEncoding(encoding);
        }
    },
    _readNext: function () {
        var file = this._stack.shift();
        if (file) {
            this._current = fs.createReadStream(file, this._opts)
                .on('data', this._onData.bind(this))
                .on('error', this._onError.bind(this))
                .on('end', this._onEnd.bind(this));
            this._current.on('close', this._onClose.bind(this, this._current));
        }
    },
    _onData: function (chunk) {
        this.emit('data', chunk);
    },
    _onClose: function (stream) {
        this.emit('close', stream);
    },
    _onError: function (err) {
        this.emit('error', err);
    },
    _onEnd: function () {
        this._current.removeAllListeners().destroy();
        this._current = undefined;
        if (this._stack.length === 0) {
            this.readable = false;
            this.emit('end');
        } else {
            this._readNext();
        }
    },
    destroy: function () {
        if (this._current) {
            this._current.removeAllListeners().destroy();
            this._current = undefined;
        }
        this.readable = false;
        this._stack = [];
    }
});

ComboStream.createCombo = function (files, opts) {
    return new ComboStream(files, opts);
};

module.exports = ComboStream;

server.js

var combo = require('./combo.js'),
    http = require('http'),
    zlib = require('zlib');

http.createServer(function (req, res) {
    if (req.url == '/') {
        res.writeHead(200, {
            'Content-Type': 'application/javascript',
            'content-encoding': 'deflate'
        });
        combo.createCombo(['hello.js', 'world.js']).pipe(zlib.createDeflate()).pipe(res);
    } else {
        res.end();
    }
}).listen(3000, '127.0.0.1');
console.log('Server running at http://127.0.0.1:3000/');

It's probably a bad idea because it reads files sequentially