The many ways to manage dependencies in YUI3

yui.loader.js

// Add modules globally
(function () {
  var cfg = window.YUI_config || {};
  
  cfg.modules = cfg.modules || {};
  
  // Add external dependencies
  cfg.modules.externalDependency = {
    fullpath: '/path/to/script.js',
    requires: ['node', 'event']
  };
  
  // Add CSS dependencies
  cfg.modules.cssDependency = {
    fullpath: '/path/to/styles.css',
    type: 'css'
  };
  
  // Set up your own rollup
  cfg.groups = cfg.groups || {};
  cfg.groups.myNameSpace = {
    combine: true, // or false
    comboBase: 'http://www.mysite.com/combo.php',
    base: 'http://www.mysite.com/scripts/',
    modules: {
      module1: { path: 'module1.js'},
      css1: { path: 'css1.css'},
      module2: { path: 'module2.js', requires: ['module1', 'css1']}
    } 
  };

  window.YUI_config = cfg;
}());
YUI().use('externalDependency', 'cssDependency', 'module2', function (Y) {
  // Your application code
}); 

// Add modules at the sandbox level
YUI({
  modules: {
    sandboxOnly: { fullpath: '/path/to/script.js' }
  }
}).use(function (Y) {
  // Your application code
});

// Add modules at runtime
YUI().use(function (Y) {
  YUI_config.modules.runtimeModule = {
    fullpath: '/path/to/script', requires: ['node']
  };
  Y.applyConfig(YUI_config);
  Y.use('runtimeModule', function (Y2) { // Y2 === Y
    // Your application code
  });
});