How extjs Ext.require () works

I understand that let's say if we have

Ext.require([
  'Ext.ux.grid.FiltersFeature',
  'Ext.toolbar.Paging'
]);

it will translate these entries to some_path / ux / grid / FilterFeature.js etc.

but how

Ext.require([
  'Ext.grid.*',
]);

will work? he knows how many js files are below the grid / directory, so on the client side, how can he download them ?, it's kind of lazy loading, I mean, if some other file has a js child entry, it will allow download?

thank