Catching Tabs in TextArea

Question

Does anyone know a cross-browser, reliable solution for catching presses of the tab-key in a textarea field, and replacing (in the correct position) 4 spaces? The textarea is being used to input an essay, and needs this feature.

Note: I tried using FCKEditor, among others, which did not catch tabs and had a bunch of features I didn't need. I want a simple solution just for catching tabs.

Answer 1

I didn't test extensively, but this seems to work:

(I found the "insertAtCursor" function at http://alexking.org/blog/2003/06/02/inserting-at-the-cursor-using-javascript#comment-3817)

<textarea id="text-area" rows="20" cols="100"></textarea>

<script>
document.getElementById("text-area").onkeydown = function(e) {
  if (!e && event.keyCode == 9)
  {
    event.returnValue = false;
    insertAtCursor(document.getElementById("text-area"), "    ");
  }
  else if (e.keyCode == 9)
  {
    e.preventDefault();
    insertAtCursor(document.getElementById("text-area"), "    ");
  }
};

//http://alexking.org/blog/2003/06/02/inserting-at-the-cursor-using-javascript#comment-3817
function insertAtCursor(myField, myValue) {
  //IE support
  if (document.selection) {
    var temp;
    myField.focus();
    sel = document.selection.createRange();
    temp = sel.text.length;
    sel.text = myValue;
    if (myValue.length == 0) {
      sel.moveStart('character', myValue.length);
      sel.moveEnd('character', myValue.length);
    } else {
      sel.moveStart('character', -myValue.length + temp);
    }
    sel.select();
  }
  //MOZILLA/NETSCAPE support
  else if (myField.selectionStart || myField.selectionStart == '0') {
    var startPos = myField.selectionStart;
    var endPos = myField.selectionEnd;
    myField.value = myField.value.substring(0, startPos) + myValue + myField.value.substring(endPos, myField.value.length);
    myField.selectionStart = startPos + myValue.length;
    myField.selectionEnd = startPos + myValue.length;
  } else {
    myField.value += myValue;
  }
}
</script>

EDIT: Modified the script so it doesn't use jQuery.