Question

我似乎无法正确地将语法正确添加到专辑ID 5439的值为“ABBA”的新“艺术家”字段，我不断收到未定义“艺术家”的错误，这是有道理但无论哪个我正确的插入方式我似乎错了。

代码用于检查值是否为track并为空，然后使用value变量中的值添加传入的新属性变量。我想用JSON你可以用obj.prop =“value”添加;但这似乎没有用

// Setup
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"
    }
};
// Keep a copy of the collection for tests
var collectionCopy = JSON.parse(JSON.stringify(collection));

// Only change code below this line
function updateRecords(id, prop, value) {

  if(prop !== "tracks" && value !== null){
    collection.id[prop] = prop[value];
  }


  return collection;
}

// Alter values below to test your code
updateRecords(5439, "artist", "ABBA");

Answer 1

您收到的错误是：

VM5865：33未捕获的TypeError：无法设置'artist'的属性undefined

这意味着collection.id为undefined。这是有道理的，因为collection没有id属性。

您还设置了错误的value。

替换：

collection.id[prop] = prop[value];

使用：

collection[id][prop] = value;

collection[id]是您需要的集合。 [prop]用于定位集合的"artist"属性。 value是您要存储为"artist"的值。

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" } };
// Keep a copy of the collection for tests
var collectionCopy = JSON.parse(JSON.stringify(collection));

// Only change code below this line
function updateRecords(id, prop, value) {

  if (prop !== "tracks" && value !== null) {
    collection[id][prop] = value;
  }

  return collection;
}

// Alter values below to test your code
var result = updateRecords(5439, "artist", "ABBA");
console.log(result['5439'])

Answer 2

collection.id[prop] = prop[value];

Collection没有名为id的属性。 id是直接收集对象的属性。

collection[id][prop] = prop[value];

将新值传递给对象

2 个答案: