code: function loadModule(moduleId) {
          // 加载过的模块，就不要再继续了
          if (loadingModules[moduleId] || modModules[moduleId]) {
              return;
          }
          loadingModules[moduleId] = 1;
  
          // 初始化相关 shim 的配置
          var shimConf = requireConf.shim[moduleId];
          if (shimConf instanceof Array) {
              requireConf.shim[moduleId] = shimConf = {
                  deps: shimConf
              };
          }
  
          // shim依赖的模块需要自动标识为shim
          // 无论是纯正的shim模块还是hybird模块
          var shimDeps = shimConf && (shimConf.deps || []);
          if (shimDeps) {
              each(shimDeps, function (dep) {
                  if (!requireConf.shim[dep]) {
                      requireConf.shim[dep] = {};
                  }
              });
              actualGlobalRequire(shimDeps, load);
          }
          else {
              load();
          }
  
          /**
           * 发送请求去加载模块
           *
           * @inner
           */
          function load() {
              /* eslint-disable no-use-before-define */
              var bundleModuleId = bundlesIndex[moduleId];
              createScript(bundleModuleId || moduleId, loaded);
              /* eslint-enable no-use-before-define */
          }
  
          /**
           * script标签加载完成的事件处理函数
           *
           * @inner
           */
          function loaded() {
              if (shimConf) {
                  var exports;
                  if (typeof shimConf.init === 'function') {
                      exports = shimConf.init.apply(
                          global,
                          modGetModulesExports(shimDeps, BUILDIN_MODULE)
                      );
                  }
  
                  if (exports == null && shimConf.exports) {
                      exports = global;
                      each(
                          shimConf.exports.split('.'),
                          function (prop) {
                              exports = exports[prop];
                              return !!exports;
                          }
                      );
                  }
  
                  globalDefine(moduleId, shimDeps, function () { 
                      return exports || {};
                  });
              }
              else {
                  modCompletePreDefine(moduleId);
              }
  
              modAutoDefine();
          }
      }
docs: 加载模块
  
  @inner
  @param {string} moduleId 模块标识