code: function require(parent, id, fn) {
  		if (fn) { return ensure(parent, id, fn); }
  		var module = getModule(parent, id);
  		if (!module.loaded) { throw new Error(id + ' not found'); }
  		if (!('exports' in module)) {
  			module.parent = parent; // first module to actually require this one is parent
  
  			// if define was passed a non-function, just assign it to exports
  			if ('function' !== typeof factories[id = module.id]) { module.exports = factories[id]; }
  			else {
  				module.exports = {};
  				fn = map(module.children.slice(0, factories[id].length), // don't require prematurely on wrapped commonjs
  						function(child) { return require(module, child.id); });
  				if ((fn = factories[id].apply(global, fn))) { module.exports = fn; } // if something was returned, export it instead
  			}
  		}
  		return module.exports;
  	}
docs: execute a module's code, and return its exports