《DOM Scripting》 suggest function

addLoadEvent.js

//add function to run after windown.onload
function addLoadEvent(func) {
    var oldonload = window.onload;
    if (typeof window.onload != 'function') {
        window.onload = func;
    } else {
        window.onload = function() {
            oldonload();
            func();
        }
    }
}

insertAfter.js

//JavaScript DOM only have insert one element before another function called "insertBefore", this for insert one after another
function insertAfter(newElement, targetElement) {
    var parent = targetElement.parentNode;
    if (parent.lastChild === targetElement) {
        parent.appendChild(newElement);
    } else {
        parent.insertBefore(newElement, targetElement.nextSibling);
    }
}