FCC高级编程篇之Record Collection

Record Collection

You are given a JSON object representing a part of your musical album collection. Each album has several properties and a unique id number as its key. Not all albums have complete information.
Write a function which takes an album's id (like 2548), a property prop (like "artist" or "tracks"), and a value (like "Addicted to Love") to modify the data in this collection.
If prop isn't "tracks" and value isn't empty (""), update or set the value for that record album's property.
Your function must always return the entire collection object.
There are several rules for handling incomplete data:
If prop is "tracks" but the album doesn't have a "tracks" property, create an empty array before adding the new value to the album's corresponding property.
If prop is "tracks" and value isn't empty (""), push the value onto the end of the album's existing tracks array.
If value is empty (""), delete the given prop property from the album.

对JS对象的增删改查

题目给的原始数据为

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"
    }
};

规则有四：

1. 如果输入属性不是tracks并且值不为空，则添加或更新专辑的属性;

2. 当专辑没有tracks属性时，添加该属性，设置其值为空数组;

3. 如果有tracks属性并且值不为空，则在末尾追加新值;

4. 如果值为空，则删除该属性;

一步一步来，先处理没有值的情况:

function updateRecords(id, prop, value) {
  if (!value) {
    delete collection[id][prop];
  }

  return collection;
}

当值为空时，删除对应的属性。

然后处理属性不是tracks时的情况：

function updateRecords(id, prop, value) {
  if (!value) {
    delete collection[id][prop];
  } else if (prop !== 'tracks') {
    collection[id][prop] = value;
  }

  return collection;
}

接着处理prop是tracks时的情况：

1. 当没有tracks属性时，按照题目要求，先添加其值为空数组;

2. 添加新值;

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

  return collection;
}

现在对所写代码进行测试，结果如下图所示。