How to find the nearest common ancestors of two or more nodes?

Question

Users selects two or more elements in a HTML page. What i want to accomplish is to find those elements\' common ancestors (so body node would be the common ancestor if none

Answer 1

Here is a dirtier way of doing this. It's easier to understand but requires dom modification:

function commonAncestor(node1,node2){
        var tmp1 = node1,tmp2 = node2;
        // find node1's first parent whose nodeType == 1
        while(tmp1.nodeType != 1){
            tmp1 = tmp1.parentNode;
        }
        // insert an invisible span contains a strange character that no one 
        // would use
        // if you need to use this function many times,create the span outside
        // so you can use it without creating every time
        var span = document.createElement('span')
            , strange_char = '\uee99';
        span.style.display='none';
        span.innerHTML = strange_char;
        tmp1.appendChild(span);
        // find node2's first parent which contains that odd character, that 
        // would be the node we are looking for
        while(tmp2.innerHTML.indexOf(strange_char) == -1){
            tmp2 = tmp2.parentNode; 
        }                           
        // remove that dirty span
        tmp1.removeChild(span);
        return tmp2;
    }