Fastest way to add new nodes to the DOM

frag.js

var frag = document.createDocumentFragment();

ajaxResult.items.forEach(function(item) {
    // Create the LI element
    var li = document.createElement('li');
    li.innerHTML = item.text;

    // Do some normal node operations on the LI here,
    // like add classes, modify attributes, 
    // add event listeners, add child nodes, etc.

    // *Instead place the LI into the fragment*
    frag.appendChild(li);
});

// Lastly, mass-inject all list items via the DocumentFragment
document.querySelector('ul').appendChild(frag);