gistfile1.js

var Require = function() {
	function NativeRequire(module) {
		var source;
		// read source from file

		if (!FS) {
			source = imports.FSREAD("modules/fs.js");
			FS = Function.apply(Function,imports_names.concat([source])).apply(Function,imports_funcs);
		}
		
		if (module !== "fs") {
			source = FS.read("modules/"+module+".js");
			return Function.apply(Function,imports_names.concat([source])).apply(Function,imports_funcs);
		}
		return FS;
	}
	
	function SubClass(){}
	NativeRequire.prototype = SubClass.prototype;
	NativeRequire.prototype.constructor = Require;
			
	return NativeRequire;
};
	
var myrequire = new Require();

require("something"); // works

console.log(myrequire.constructor === Require);