Get all classes and IDs of DOM elements given a parent element

getClassesAndIds.js

function getClassesAndIds(parent, memo) {
    if (typeof memo === 'undefined')
        memo = {classes: [], ids: []};
    
    if (parent.className)
        parent.className.split(' ').forEach(function (className) {
            if (className && !~memo.classes.indexOf(className))
                memo.classes.push(className)
        });

    if (parent.id)
        memo.ids.push(parent.id);

    [].forEach.call(parent.childNodes, function (node) {
        memo = getClassesAndIds(node, memo)
    });

    return memo;
}