text: function whatIsInAName(collection, source) {
  
    var srcKeys = Object.keys(source);
  
    // filter the collection
    return collection.filter(function (obj) {
      for(var i = 0; i < srcKeys.length; i++) {
        if(!obj.hasOwnProperty(srcKeys[i]) || obj[srcKeys[i]] !== source[srcKeys[i]]) {
          return false;
        }
      }
      return true;
    });
  }
  
  whatIsInAName([{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, { first: "Tybalt", last: "Capulet" }], { last: "Capulet" });
  