For next loop step up down

How to use for in google asp script

• Countup step = 1 
• Countup step = 2 or more
• Countdown step = 1

For with Step 1

function forTest1() {
     var ss = SpreadsheetApp.getActiveSpreadsheet();
     var sheet = ss.getSheets()[0];

  for (var i = 1; i < 5; i++) {
    var range = sheet.getRange(8,i);
    var data = range.setValue(i); 
  }
}

For with Step 2

function forTest2() {
     var ss = SpreadsheetApp.getActiveSpreadsheet();
     var sheet = ss.getSheets()[0];
  // step = 2 (or more)
  for (var i = 1; i < 10; i=i+2) {
    var range = sheet.getRange(9,i);
    var data = range.setValue(i); 
  }
}

For with countdown loop

function forTest3() {
     var ss = SpreadsheetApp.getActiveSpreadsheet();
     var sheet = ss.getSheets()[0];

  for (var i = 10; i > 3; i=i-1) {
    var range = sheet.getRange(11,i);
    var data = range.setValue(i); 
  }
}