Adobe Acrobat javascript loop to erase every 2nd and 3rd checkbox

I'm attempting to convert a handful of wingdings to checkbox form fields within Adobe Acrobat, and then erase each 2nd and 3rd checkbox with a loop akin to this.eraseField(["CheckBox1, CheckBox2, CheckBox4, CheckBox5]); and so on for all checkboxes.

I've hacked together this code, but loops are my weakness.

for (var i = 0; i < this.numFields; i++) {
    var f = this.getField(this.getNthFieldName(i));

    if (f != null && i % 3 != 0) {
    this.removeField("f");
    }
}

I know I'm doing this wrong, I cannot figure out how to correctly set up this loop. Any help would be appreciated.