How to get the caret column (not pixels) position in a textarea, in characters, from the start?

Question

How do you get the caret position in a <textarea> using JavaScript?

For example: This is| a text

This should return 7.

How would you get it to return the strings surrounding the cursor / selection?

E.g.: 'This is', '', ' a text'.

If the word “is” is highlighted, then it would return 'This ', 'is', ' a text'.

Answer 1

With Firefox, Safari (and other Gecko based browsers) you can easily use textarea.selectionStart, but for IE that doesn't work, so you will have to do something like this:

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;
}

(complete code here)

I also recommend you to check the jQuery FieldSelection Plugin, it allows you to do that and much more...

Edit: I actually re-implemented the above code:

function getCaret(el) { 
  if (el.selectionStart) { 
    return el.selectionStart; 
  } else if (document.selection) { 
    el.focus(); 

    var r = document.selection.createRange(); 
    if (r == null) { 
      return 0; 
    } 

    var re = el.createTextRange(), 
        rc = re.duplicate(); 
    re.moveToBookmark(r.getBookmark()); 
    rc.setEndPoint('EndToStart', re); 

    return rc.text.length; 
  }  
  return 0; 
}

Check an example here.