Illustrator Scripting :: How To Extract Text In Order From Top Left To Bottom Right

I want to extract all the texts in a illustrator file to a txt file. which could be done like this:
 
var docObj=app.activeDocument;
var tfObj=docObj.textFrames;
var myTextFrames = [];
for(var m=0; m < tfObj.length; m++){
myTextFrames.push(tfObj[m].contents);
}
  
But since the text frames were extracted by create order, not by layout, I want to ajust the oder from top left to bottom right first, then export.
 
I thought it could be done by selecting all the text frames first, then sorting the selection orders by loop. But I don't know how to select all the text frames, and not sure whether this is the right way...