Check duplicate html element ID on the page

gistfile1.js

(function findDuplicateIds(){
    var ids = {};
    var all = document.all || document.getElementsByTagName("*");
    for(var i=0, l=all.length; i<l; i++){
        var id = all[i].id;
        if(id){
            if(ids[id]){
                console.log("Duplicate id: #" + id);
            } else {
                ids[id] = 1;
            }
        }
    }
})();