Question: Is it possible to use `require()` (or something similar) on client side?

**Example**

```
var myClass = require('./js/myclass.js');

```

Answer: 
Take a look at [requirejs](http://requirejs.org/) project.
Some answers already - but I would like to point you to YUI3 and its on-demand module loading. It works on both server (node.js) and client, too - I have a demo website using the exact same JS code running on either client or server to build the pages, but that's another topic.

YUI3: <http://developer.yahoo.com/yui/3/>

Videos: <http://developer.yahoo.com/yui/theater/>

Example:

(precondition: the basic YUI3 functions in 7k yui.js have been loaded)

```
YUI({
    //configuration for the loader
}).use('node','io','own-app-module1', function (Y) {
    //sandboxed application code
    //...

    //If you already have a "Y" instance you can use that instead
    //of creating a new (sandbox) Y:
    //  Y.use('moduleX','moduleY', function (Y) {
    //  });
    //difference to YUI().use(): uses the existing "Y"-sandbox
}

```

This code loads the YUI3 modules "node" and "io", and the module "own-app-module1", and then the callback function is run. A new sandbox "Y" with all the YUI3 and own-app-module1 functions is created. Nothing appears in the global namespace. The loading of the modules (.js files) is handled by the YUI3 loader. It also uses (optional, not show here) configuration to select a -debug or -min(ified) version of the modules to load.