addOnload(initFoo);

function addOnload(newFunction) {
    var oldOnload = window.onload;
    
    if (typeof oldOnload == "function") {
        window.onload = function() {
            if (oldOnload) {
                oldOnload();
            }
            newFunction();
        }
    }
    else {
        window.onload = newFunction;
    } 
}