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 lookUpProfile(firstName, prop){

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

}


lookUpProfile("Akira", "likes");

可出运行啊：
document.write(lookUpProfile("Akira", "likes"));