Find duplicated id attributes

DuplicatedIdAttribute.js

var ids = {}; 
var elementsWithId = document.querySelectorAll("[id]");
Array.prototype.forEach.call(elementsWithId, function(el){
  var id = el.id; 
  if(ids[id]){
    ids[id]++;
  }else{
    ids[id]=1;
  }
}); 
Object.keys(ids).forEach(function(key){
  if(key && ids[key]>1){
    console.log(key+" : " + ids[key]);
  } 
})