How to for plugin development

// Apply the given function to all notes in selection
// or, if nothing is selected, in the entire score
function applyToNotesInSelection(func) {
      if (typeof curScore === 'undefined')
            return;

      var cursor     = new Cursor(curScore);
      cursor.goToSelectionStart();
      var startStaff  = cursor.staff;
      cursor.goToSelectionEnd();
      var endStaff   = cursor.staff;
      var endTick    = cursor.tick() // if no selection, end of score
 
      if (cursor.eos()) { // no selection
            startStaff = 0; // start with 1st staff
            endStaff = curScore.staves; // and end with last
      }

      for (var staff = startStaff; staff < endStaff; ++staff) {
            for (var voice = 0; voice < 4; voice++) {          
                  cursor.goToSelectionStart(); // sets voice to 0
                  cursor.voice = voice; //voice has to be set after goTo
                  cursor.staff = staff;
                  if (cursor.eos())
                          cursor.rewind() // if no selection, beginning of score

                  while (cursor.tick() < endTick) {
                        if (cursor.isChord()) {
                              var chord = cursor.chord();
                              var n     = chord.notes;
                              for (var i = 0; i < n; i++) {
                                    var note   = chord.note(i);
                                    func(note);
                              }
                        }
                        cursor.next();
                  }
            }
      }
}

//---------------------------------------------------------
//    init
//    this function will be called on startup of mscore
//---------------------------------------------------------

function init()
      {
      }

//-------------------------------------------------------------------
//    run
//    this function will be called when activating the
//    plugin menu entry
//-------------------------------------------------------------------

function run()
      {
      // temp folder for user  C:\Users\<USERNAME>\AppData\Local\Temp on windows
      var path = QDir.tempPath(); // 
      var file = path + "/score.ly";
      curScore.save(file, "ly");
      
      //See http://doc.qt.nokia.com/latest/qprocess.html
      var lilypond = new QProcess();
      var args = new Array();
      args[0]= "-o";
      args[1]= path;
      args[2]= file;
      
      // if you want to log output
      //lilypond.setStandardOutputFile("stdout.txt");
      //lilypond.setStandardErrorFile("stderr.txt");

      lilypond.start("lilypond", args );
      lilypond.waitForStarted();
      lilypond.waitForFinished();
      }

//---------------------------------------------------------
//    menu:  defines were the function will be placed
//           in the MuseScore menu structure
//---------------------------------------------------------

var mscorePlugin = {
      menu: 'Plugins.Lilypond process',
      init: init,
      run:  run
      };

mscorePlugin;