DOM manipulation

gistfile1.js

function firstElementChild(e) {
    var e = e || document.documentElement;
    return e.firstElementChild || e.children[0] || null;
}
function lastElementChild(e) {
    var e = e || document.documentElement;
    return e.lastElementChild || e.children[e.children.length-1] || null;
}
function nextElementSibling(e) {
    if(e.nextElementSibling) return e.nextElementSibling;
    for(e = e.nextSibling; e && e.nodeType !== 1; e = e.nextSibling);
    return e;
}
function previousElementSibling(e) {
    if(e.previousElementSibling) return e.previousElementSibling;
    for(e = e.previousSibling; e && e.nodeType !== 1; e = e.previousSibling);
    return e;
}