attempt to move dupes to end of list

test2.js

const someCollection = [{
 results: [
   {
     name: 'alpha',
     region : {
       region_id : 1234
     }
   },
   {
     name: 'beta',
     region : {
       region_id : 1
     }
   },
   {
     name: 'this should move to bottom',
     region : {
       region_id : 1234
     }
   }
 ] 
}];

function transformCollection(someCollection) {
  // if collection has results
  if (someCollection[0].results) {
    // create hashmap
    let exists = {};
    // create a new list
    let parsedList = [];
    // create duped list
    let dupedList = [];
    
    
    someCollection[0].results.forEach(item => {
      if (exists[item.region.region_id]) {
        dupedList.push(item);
      } else {
        exists[item.region.region_id] = true;
        parsedList.push(item);
      }      
    });
    
    console.log(parsedList.concat(dupedList));
    return parsedList.concat(dupedList);
  }
  
}

transformCollection(someCollection);