javascript - How to construct many .js files to one file under same namespace -

i have 1 .js file, code under 1 namespace:

var somenamespace = somenamespace || {};  (function () {    "use strict";      ...      //some code here      ... }).apply(somenamespace); 

i want separate logic many .js files , main .js, on load, construct 1 .js file separated files under 1 scope shared parameters , private functions.

i can't use libraries task requirejs , must pure javascript.

so best practice that?