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Several public CDNs host popular JS libs, most notably Until now there was no easy way to combo the various libs into a single URL in order to maximize performance. This package fills that gap by generating and serving combo URLs across various CDNs and any other public server.


$ npm i cmbn


This software is currently demoed at but there are no guarantees to availability. It's recommended to install cmbn on your own host in order to enable comboing with application-specific assets. To maximize performance even further cmbn should be fronted by a CDN like CloudFlare.

Standalone server

var cmbn = require('cmbn');

In addition to the options available for middleware ,createServer accepts one or more of the following:

  • port - Port to listen on. Default is 80.
  • staticDir - Directory to serve static assets from. Particularly useful if comboing from localhost.
  • staticMaxAge - Number of seconds to set for maxAge in the Cache-Control header if serving local assets.


var connect = require('connect'),
    express = require('express'),
    cmbn = require('cmbn'),
    app = express.createServer();


middleware takes an optional argument which is an object containing one or more of the following:

  • cacheSize - The size in bytes to reserve for the lru-cache which stores external assets which have been fetched. Default is 5000000 (~5MB).
  • cacheFunc -The cache function used to determine the size of each asset, default is to return item.length.

Node Client

var cmbn = require('cmbn'),
    url = cmbn.client.combine([


combine also takes an optional argument which is an object containing one or more of the following:

  • host - The hostname[:port] which is running cmbn. Defaults to (see note under Usage).
  • protocol - The protocol for the host running cmbn. Defaults to http.

Browser Client

<script src=""></script>
var url = cmbn.client.combine([


See Node Client.

Adding a CDN

var cmbn = require('cmbn');
// add cdn for localhost
cmbn.cdns.addCdn('lh', {host: 'localhost:8080', prefix: 'libs/'});

var url = cmbn.client.combine([
], {host: 'localhost:8080'});

// http://localhost:8080/~gg;jquery,1.7.2,jquery.min.js/~lh;cmbn,0.0.1,cmbn.min.js

Run the Example

After installing the package run node examples from the package root. A link will be output by the client and the server will start. Copy the link and paste it into a browser to see the comboed output.


See the examples folder and code for more usage information.


MIT License. See the accompanying LICENSE file for terms.