if/else问题？

var contacts = [
{
    "firstName": "Akira",
    "lastName": "Laine",
    "number": "0543236543",
    "likes": ["Pizza", "Coding", "Brownie Points"]
},
{
    "firstName": "Harry",
    "lastName": "Potter",
    "number": "0994372684",
    "likes": ["Hogwarts", "Magic", "Hagrid"]
},
{
    "firstName": "Sherlock",
    "lastName": "Holmes",
    "number": "0487345643",
    "likes": ["Intriguing Cases", "Violin"]
},
{
    "firstName": "Kristian",
    "lastName": "Vos",
    "number": "unknown",
    "likes": ["Javascript", "Gaming", "Foxes"]
}
];

function lookUp(firstName, prop){
  for(var i = 0;i<contacts.length;i++){
     if(contacts[i].firstName !== firstName){
        return "No such contact";
      }else{
          if(contacts[i].hasOwnProperty(prop)){
          return contacts[i][prop];
         }else{
             return "No such property";
           }
        } 
    }
   }

问题：lookUp("Kristian", "lastName");总是会回到 return "No such contact";想不通是什么原因