遍历 DOM 节点

dom.js

/* 深度优先 */
function dom1(el, isBack) {
    isBack || ++idx;
    if (!el) {
        return;
    }
    var next = isBack ? el.nextElementSibling : (el.firstElementChild || el.nextElementSibling);
    return dom1(next ? next : el.parentNode, !next);
}

/* 广度优先 */
function dom2(el, queue) {
    queue || (++idx, queue = [el]);
    var next = null;
    if (!el) {
        el = queue.shift();
        if (!el) {
            return;
        }
        next = el.firstelementchild;
    } else {
        next = el.nextelementsibling;
    }
    next && queue.push(next) && ++idx;
    return dom2(next, queue);
}