Removing x number of characters from the caret position in tinyMCE - tinymce

Question

I am working on a project where the user can enter a special character and then tab to auto complete the values. This part is mostly working, but I want to be able to delete x number of characters from before the caret position.
E.g. if | is the caret and I have the following text #chr|.
I want to be able to delete 3 characters before the cursor position, e.g. I would just end up with #.
I have found a way to get the current cursor position using the below code, but I haven't been able to find any way of being able to delete x number of characters from that position.
function getCaretPosition()
{
var ed = tinyMCE.get('txtComment'); // get editor instance
var range = ed.selection.getRng().startOffset; // get range
return range;
}

Answer 1

You can do this by creating a Range ending at the current caret position:
var ed = tinyMCE.get("mce_0"); // get editor instance
var editorRange = ed.selection.getRng(); // get range object for the current caret position
var node = editorRange.commonAncestorContainer; // relative node to the selection
range = document.createRange(); // create a new range object for the deletion
range.selectNodeContents(node);
range.setStart(node, editorRange.endOffset - 3); // current caret pos - 3
range.setEnd(node, editorRange.endOffset); // current caret pos
range.deleteContents();
ed.focus(); // brings focus back to the editor
To use the demo, position the caret somewhere in the text and then click the "Remove 3" button at the top to delete the preceding 3 characters.
Note that my demo is simplified and doesn't do any bounds checking.
Demo: http://codepen.io/anon/pen/dWVWYM?editors=0010
Compatibility is IE9+