Mutation Observer - filtered node inserted callback

gistfile1.js

function filteredNewNodeCallback(root, selector, callback) {
    var obs, i;

    if (!root || !selector || !callback) {
        return;
    }

    function filterAndCallback(node) {
        var matches = [], childMatches;
        if (node.matches(selector)){
            matches.push(node);
        }
        childMatches = node.querySelectorAll(selector);
        if (childMatches.length !== 0) {
            matches = matches.concat([].slice.call(childMatches))
        }
        matches.map(callback);
    }

    obs = new MutationObserver(function(mutations){
        mutations.forEach(function(mutation){
            for(i = 0; i < mutation.addedNodes.length; i++) {
                if (mutation.addedNodes[i].nodeType === 1) {
                    filterAndCallback(mutation.addedNodes[i]);
                }
            }
        })
    });
    obs.observe(root, {childList: true, subtree: true});
}

/* test stuff */

//make new tweets on twitter red
filteredNewNodeCallback(document.querySelector('#timeline'), '.js-stream-item', function(tweet){
    tweet.style.background = 'red';
});

Hi,

I'm trying to do something like this.

But for some reason its not working.

Any suggestions ?

   var $target = $('#timeline')
   new MutationObserver(() => console.log('hell yeahhhh'))
          .observe($target.get(0), {childList: true,subtree: true});