Various require() use cases with proposed new Brackets module loader (https://github.com/adobe/brackets/wiki/Extension-API-Research)

CoreModule.js

/*jslint vars: true, plusplus: true, devel: true, nomen: true, indent: 4 */
/*global exports, require */

(function () {
    "use strict";

    var CommandManager = require("command/CommandManager"),
        Menus          = require("command/Menus");

    
    function handleCoreCommand() {
        // ...
    }
    function usefulCoreAPI() {
        // ...
    }
    
    
    // Register command
    var COMMAND_ID = "brackets.foo";
    CommandManager.register("Foo", COMMAND_ID, handleCoreCommand);

    // Create menu item
    Menus.getMenu(Menus.AppMenuBar.FILE_MENU).addMenuItem(COMMAND_ID);
    
    
    // Expose an API - usable by other core modules & any extensions
    exports.usefulCoreAPI = usefulCoreAPI;
}());

CoreModule_jsHint.js

/*jshint globalstrict: true, vars: true, plusplus: true, devel: true, nomen: true, indent: 4 */
/*global exports, require */

"use strict";

var CommandManager = require("command/CommandManager"),
    Menus          = require("command/Menus");


function handleCoreCommand() {
    // ...
}
function usefulCoreAPI() {
    // ...
}


// Register command
var COMMAND_ID = "brackets.foo";
CommandManager.register("Foo", COMMAND_ID, handleCoreCommand);

// Create menu item
Menus.getMenu(Menus.AppMenuBar.FILE_MENU).addMenuItem(COMMAND_ID);


// Expose an API - usable by other core modules & any extensions
exports.usefulCoreAPI = usefulCoreAPI;

extension_package.json

{
    "name": "pflynn.bar",
    "title": "Bar Extension",
    "author": "Peter Flynn",
    "version": "1.0.0",
    "engines": { "brackets": ">= 0.30" },
    "peerDependencies": {
        "gruehle.someotherextension": "1.x"
    },
    "description": "Does something really awesome called 'Foo'"
}

ExtensionModule.js

/*jslint vars: true, plusplus: true, devel: true, nomen: true, indent: 4 */
/*global exports, require */

(function () {
    "use strict";

    // Load core modules
    var CommandManager = require("command/CommandManager"),
        Menus          = require("command/Menus");
    
    // Other modules within same extension
    var MyUtils        = require("./utils/MyUtils");
    
    // Load modules from other extension
    // Only works if dependency is declared in package.json!
    var BazService     = require("gruehle.someotherextension/utils/BazService");

    
    function handleExtensionCommand() {
        // ...
    }
    function barService() {
        // ...
    }
    
    
    // Register command
    var COMMAND_ID = "pflynn.bar";
    CommandManager.register("Bar", COMMAND_ID, handleExtensionCommand);

    // Create menu item
    Menus.getMenu(Menus.AppMenuBar.FILE_MENU).addMenuItem(COMMAND_ID);
    
    
    // Expose an API - usable by other extensions
    exports.barService = barService;
}());