var doc = app.activeDocument;

// 1. Obtain a reference to the '[None]' Object Style.
var noneObjectStyle = doc.objectStyles.itemByName('[None]');

// 2. Draw a rectangle
var rectangle = doc.pages[0].rectangles.add({
  geometricBounds: [0, 0, 50, 50],
  appliedObjectStyle: noneObjectStyle // <-- 3. Set its Object Style to [None].
  // ...
});