textarea-caret-position.js

function getCaret(node) {
  if (node.selectionStart) {
    return node.selectionStart;
  } else if (!document.selection) {
    return 0;
  }
  var c = "\001",
      sel = document.selection.createRange(),
      dul = sel.duplicate(),
      len = 0;

  dul.moveToElementText(node);
  sel.text = c;
  len = dul.text.indexOf(c);
  sel.moveStart('character',-1);
  sel.text = "";
  return len;
}