function whatIsInAName(collection, source) {
  // What's in a name?
  var arr = [];

  function checkSource(item) {
    return source.every(function(source) {

    });

  }
  // Only change code below this line
  arr = collection.filter(checkSource);

  // Only change code above this line
  return arr;
}

whatIsInAName([{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, { first: "Tybalt", last: "Capulet" }], { last: "Capulet" });