I need a script that would provide leading to different text frames.

This this sample script which works on a selection of text frames:

#target illustrator

function test(){

  var doc = app.activeDocument;

  var s = doc.selection;

  if(s == null && s.length == 0){

    return;

  }

  for(var i = 0; i < s.length;  i++){

    if(s.typename != "TextFrame"){

      continue;

    }

    s.textRange.characterAttributes.autoLeading = false;

    s.textRange.characterAttributes.leading = 22;

  };

};

test();