Record Collection.md

Record Collection

You are given an object literal representing a part of your musical album collection. Each album has a unique id number as its key and several other properties. Not all albums have complete information.

You start with an updateRecords function that takes an object literal, records, containing the musical album collection, an id, a prop (like artist or tracks), and a value. Complete the function using the rules below to modify the object passed to the function.

Your function must always return the entire record collection object.

• If prop isn't tracks and value isn't an empty string, update or set that album's prop to value.
• If prop is tracks but the album doesn't have a tracks property, create an empty array and add value to it.
• If prop is tracks and value isn't an empty string, add value to the end of the album's existing tracks array.
• If value is an empty string, delete the given prop property from the album. Note: A copy of the recordCollection object is used for the tests.
  

## Hints - Use `bracket notation` when accessing object properties with variables.

Push is an array method you can read about on Mozilla Developer Network.

You may refer back to Manipulating Complex ObjectsIntroducing JavaScript Object Notation (JSON) for a refresher.

Before

// Setup
const recordCollection = {
  2548: {
    albumTitle: 'Slippery When Wet',
    artist: 'Bon Jovi',
    tracks: ['Let It Rock', 'You Give Love a Bad Name']
  },
  2468: {
    albumTitle: '1999',
    artist: 'Prince',
    tracks: ['1999', 'Little Red Corvette']
  },
  1245: {
    artist: 'Robert Palmer',
    tracks: []
  },
  5439: {
    albumTitle: 'ABBA Gold'
  }
};

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

updateRecords(recordCollection, 5439, 'artist', 'ABBA');

Answers

// Setup
const recordCollection = {
  2548: {
    albumTitle: 'Slippery When Wet',
    artist: 'Bon Jovi',
    tracks: ['Let It Rock', 'You Give Love a Bad Name']
  },
  2468: {
    albumTitle: '1999',
    artist: 'Prince',
    tracks: ['1999', 'Little Red Corvette']
  },
  1245: {
    artist: 'Robert Palmer',
    tracks: []
  },
  5439: {
    albumTitle: 'ABBA Gold'
  }
};

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

 if (value === '') {
    delete records[id][prop];
  } else if (prop === 'tracks') {
    records[id][prop] = records[id][prop] || []; // this is called shortcircuit evaluation, see below for explanation
    records[id][prop].push(value);
  } else {
    records[id][prop] = value;
  }
  return records;
}
updateRecords(recordCollection, 5439, 'artist', 'ABBA');

Thinking

1. The more easy is to delete the prop if no value
2. If the prop is not tracks it's easy to add the value to this prop
3. Here we need to find if the object have a property tracks if not we create this prop with a empty array and we push it the value. I use .hasOwnProperty for doing this.