获取json

var collection = {
    2548: {
      album: "Slippery When Wet",
      artist: "Bon Jovi",
      tracks: [ 
        "Let It Rock", 
        "You Give Love a Bad Name" 
      ]
    },
    2468: {
      album: "1999",
      artist: "Prince",
      tracks: [ 
        "1999", 
        "Little Red Corvette" 
      ]
    },
    1245: {
      artist: "Robert Palmer",
      tracks: [ ]
    },
    5439: {
      album: "ABBA Gold"
    }
};
// 深拷贝 collection，用于测试
var collectionCopy = JSON.parse(JSON.stringify(collection));


function update(id, prop, value) {
 if(value !==""){
   if(prop !== "tracks"){
     collection[id][prop] = value;
   }else{
      collection[id][prop].push(value);
   }
   
   
 }else{
   delete collection[id][prop];
 }

  return collection;
}

update(5439, "artist", "ABBA");