Uncaught DOMException: Failed to execute 'setStart' on 'Range': The offset is larger than the node's length

Question

The following code is often throwing an error that reads

Uncaught DOMException: Failed to execute 'setStart' on 'Range': The offset some integer is larger than the node's length (some smaller integer).

var range = document.createRange();
range.setStart(pos.node, pos.position + someNumber);

pos is set like so:

getTextNodeAtPositionAndReturnEndOfContextIfNeeded = function(root, index){
  var lastNode = null;
  var nodeCount = 0;
  var treeWalker = document.createTreeWalker(root, NodeFilter.SHOW_TEXT, function next(elem) {
    nodeCount++;
    if(index > elem.textContent.length){
      index -= elem.textContent.length;
      lastNode = elem;
      return NodeFilter.FILTER_REJECT;
    }
    return NodeFilter.FILTER_ACCEPT;
  }, true); //true was added as a parameter to satisfy ie, but I haven't determined if it still works in other browsers, seems fine in Chrome so far.
  var c = treeWalker.nextNode();
  return {
    node: c ? c : root,
    position: c ? 0 : nodeCount
  };
}

var pos = getTextNodeAtPositionAndReturnEndOfContextIfNeeded(context, len);

What I'm looking for is how to determine the node's length in advance of calling range.setStart, but I'm not sure where to access that.

I'm guessing that I can add something like this:

return {
  node: c ? c : root,
  position: c ? 0 : nodeCount,
  maxLength: root.length //<-something like this, but I have no idea what to put here
};

Answer 1

This happens because two extra adjacent text nodes are added when we add mark in parent.

So, use node.normalize to wrap the nodes.