Added feature to read tracks with multiple genres

CONTRIBUTORS.md

@@ -26,6 +26,9 @@ Donations are towards the ["Girls Who Code" NPO](https://www.classy.org/checkout
 * **[LiuTongTong](https://github.com/TongDaDa)**
   * Added ArrayBuffer file reader.
 
+* **[Denes Tornyi](https://github.com/pinting)**
+  * Added feature to read tracks with multiple genres.
+
 ## Bugs
 
 * **[Curtis Menmuir](https://github.com/curtismenmuir)**

README.md

@@ -2,6 +2,8 @@
 
 The next version of https://github.com/aadsm/JavaScript-ID3-Reader.
 
+Modified version of https://github.com/aadsm/jsmediatags as this supports tracks with multiple genres.
+
 ## Donations
 A few people have asked me about donations (or even crowdfunding). I would prefer you to consider making a donation to the ["Girls Who Code" NPO](https://www.classy.org/checkout/donation?eid=77372). If you do please send me a message so I can add you as a contributor.
 
@@ -162,74 +164,253 @@ new Promise((resolve, reject) => {
 ### The Output
 This is an example of the object passed to the `jsmediatags.read`'s `onSuccess` callback.
 
+#### ID3v1
+
+```javascript
+{
+  type: 'ID3',
+  version: '1.1',
+  tags: {
+    title: 'Sorrow Tears and Blood',
+    artist: 'Fela Kuti',
+    album: 'Opposite People / Sorrow Tears',
+    year: '1977',
+    comment: '',
+    genres: [ 'Ethnic' ],
+    genre: 'Ethnic',
+    track: 3
+  }
+}
+```
+
 #### ID3v2
 ```javascript
 {
-  type: "ID3",
-  version: "2.4.0",
-  major: 4,
+  type: 'ID3',
+  version: '2.3.0',
+  major: 3,
   revision: 0,
+  flags: {
+    unsynchronisation: false,
+    extended_header: false,
+    experimental_indicator: false,
+    footer_present: false
+  },
+  size: 64578,
   tags: {
-    artist: "Sam, The Kid",
-    album: "Pratica(mente)",
-    track: "12",
-    TPE1: {
-      id: "TPE1",
-      size: 14,
-      description: "Lead performer(s)/Soloist(s)",
-      data: "Sam, The Kid"
+    title: 'Sorrow Tears and Blood',
+    artist: 'Fela Kuti',
+    album: 'Opposite People / Sorrow Tears and Blood',
+    year: '1977',
+    track: '3/4',
+    genres: [ 'Afrobeat', 'African' ],
+    genre: 'Afrobeat',
+    picture: {
+      format: 'image/jpeg',
+      type: 'Cover (front)',
+      description: '',
+      data: [Array]
     },
     TALB: {
-      id: "TALB",
-      size: 16,
-      description: "Album/Movie/Show title",
-      data: "Pratica(mente)"
+      id: 'TALB',
+      size: 85,
+      description: 'Album/Movie/Show title',
+      data: 'Opposite People / Sorrow Tears and Blood'
+    },
+    TPE1: {
+      id: 'TPE1',
+      size: 23,
+      description: 'Lead performer(s)/Soloist(s)',
+      data: 'Fela Kuti'
+    },
+    TPE2: {
+      id: 'TPE2',
+      size: 23,
+      description: 'Band/orchestra/accompaniment',
+      data: 'Fela Kuti'
+    },
+    TCON: {
+      id: 'TCON',
+      size: 39,
+      description: 'Content type',
+      data: [Array]
+    },
+    TPUB: {
+      id: 'TPUB',
+      size: 27,
+      description: 'Publisher',
+      data: 'MCA Records'
+    },
+    TIT2: {
+      id: 'TIT2',
+      size: 49,
+      description: 'Title/songname/content description',
+      data: 'Sorrow Tears and Blood'
     },
     TRCK: {
-      id: "TRCK",
-      size: 3,
-      description: "Track number/Position in set",
-      data: "12",
+      id: 'TRCK',
+      size: 5,
+      description: 'Track number/Position in set',
+      data: '3/4'
+    },
+    UFID: {
+      id: 'UFID',
+      size: 59,
+      description: 'Unique file identifier',
+      data: [Object]
+    },
+    TYER: { id: 'TYER', size: 6, description: 'Year', data: '1977' },
+    TSOP: {
+      id: 'TSOP',
+      size: 47,
+      description: 'Performer sort order',
+      data: 'Kuti, Fela; Africa 70'
+    },
+    TSO2: {
+      id: 'TSO2',
+      size: 25,
+      description: 'Unknown',
+      data: 'Kuti, Fela'
+    },
+    TXXX: [ [Object], [Object], [Object], [Object], [Object], [Object] ],
+    APIC: {
+      id: 'APIC',
+      size: 61857,
+      description: 'Attached picture',
+      data: [Object]
     }
-  },
-  size: 34423,
-  flags: {
-    unsynchronisation: false,
-    extended_header: false,
-    experimental_indicator: false,
-    footer_present: false
+  }
+}
+{
+  type: 'MP4',
+  ftyp: 'M4A ',
+  version: 0,
+  tags: {
+    '©too': {
+      id: '©too',
+      size: 99,
+      description: 'Encoding Tool',
+      data: 'qaac 2.69, CoreAudioToolbox 7.10.9.0, AAC-LC Encoder, TVBR q127, Quality 96'
+    },
+    trkn: {
+      id: 'trkn',
+      size: 32,
+      description: 'Track Number',
+      data: [Object]
+    },
+    '©ART': { id: '©ART', size: 33, description: 'Artist', data: 'Fela Kuti' },
+    aART: {
+      id: 'aART',
+      size: 33,
+      description: 'Album Artist',
+      data: 'Fela Kuti'
+    },
+    '©nam': {
+      id: '©nam',
+      size: 46,
+      description: 'Title',
+      data: 'Sorrow Tears and Blood'
+    },
+    '©alb': {
+      id: '©alb',
+      size: 64,
+      description: 'Album',
+      data: 'Opposite People / Sorrow Tears and Blood'
+    },
+    '©day': { id: '©day', size: 28, description: 'Release Date', data: '1977' },
+    covr: {
+      id: 'covr',
+      size: 61867,
+      description: 'Cover Art',
+      data: [Object]
+    },
+    title: 'Sorrow Tears and Blood',
+    artist: 'Fela Kuti',
+    album: 'Opposite People / Sorrow Tears and Blood',
+    year: '1977',
+    track: 3,
+    picture: { format: 'image/jpeg', data: [Array] },
+    genres: [ 'Afrobeat', 'African' ],
+    genre: 'Afrobeat'
   }
 }
 ```
 
 #### MP4
 ```javascript
 {
-  type: "MP4",
-  ftyp: "M4A",
+  type: 'MP4',
+  ftyp: 'M4A ',
   version: 0,
   tags: {
-    "©too": {
-      id: "©too",
-      size: 35,
+    '©too': {
+      id: '©too',
+      size: 99,
       description: 'Encoding Tool',
-      data: 'Lavf53.24.2'
-    }
+      data: 'qaac 2.69, CoreAudioToolbox 7.10.9.0, AAC-LC Encoder, TVBR q127, Quality 96'
+    },
+    trkn: {
+      id: 'trkn',
+      size: 32,
+      description: 'Track Number',
+      data: [Object]
+    },
+    '©ART': { id: '©ART', size: 33, description: 'Artist', data: 'Fela Kuti' },
+    aART: {
+      id: 'aART',
+      size: 33,
+      description: 'Album Artist',
+      data: 'Fela Kuti'
+    },
+    '©nam': {
+      id: '©nam',
+      size: 46,
+      description: 'Title',
+      data: 'Sorrow Tears and Blood'
+    },
+    '©alb': {
+      id: '©alb',
+      size: 64,
+      description: 'Album',
+      data: 'Opposite People / Sorrow Tears and Blood'
+    },
+    '©day': { id: '©day', size: 28, description: 'Release Date', data: '1977' },
+    covr: {
+      id: 'covr',
+      size: 61867,
+      description: 'Cover Art',
+      data: [Object]
+    },
+    title: 'Sorrow Tears and Blood',
+    artist: 'Fela Kuti',
+    album: 'Opposite People / Sorrow Tears and Blood',
+    year: '1977',
+    track: 3,
+    picture: { format: 'image/jpeg', data: [Array] },
+    genres: [ 'Afrobeat', 'African' ],
+    genre: 'Afrobeat'
   }
 }
 ```
 
 #### FLAC
 ```javascript
 {
-  type: "FLAC",
-  version: "1",
+  type: 'FLAC',
+  version: '1',
   tags: {
-    title: "16/12/95",
-    artist: "Sam, The Kid",
-    album: "Pratica(mente)",
-    track: "12",
-    picture: ...
+    title: 'Sorrow Tears and Blood',
+    artist: 'Fela Kuti',
+    album: 'Opposite People / Sorrow Tears and Blood',
+    track: '3/4',
+    genres: [ 'Afrobeat', 'African' ],
+    genre: 'Afrobeat',
+    picture: {
+      format: 'image/jpeg',
+      type: 'Cover (front)',
+      description: '',
+      data: [Array]
+    }
   }
 }
 ```
@@ -262,10 +443,21 @@ These are the supported shortcuts.
 * `year`
 * `comment`
 * `track`
-* `genre`
+* `genres`
+* `genre` (first element of the genres array)
 * `picture`
 * `lyrics`
 
+### Multiple genres
+
+FLAC and MP4 supports multiple genre fields.
+
+ID3v1 supports only one genre field and it stores the information in one byte (and uses a predefined list to translate the value back to human readable information), so storing multiple genres is not an option.
+
+ID3v2 supports only one genre field, but up to 16MB in length, so the different genres can be stored joined with a special character. The most common approach is to use the character `65279` as a separator.
+
+Mp3tag does all the required work automatically if the supplied genres are separated with double backslash (`\\`) characters. For example, to have `["Afrobeat", "African"]` in the output of `jsmediatags`, the Genre field of Mp3tag needs to contain the following: `Afrobeat\\African`. This will work with FLAC, MP4 and ID3v2 as well.
+
 ### Picture data
 
 The `picture` tag contains an array buffer of all the bytes of the album artwork image as well as the content type of the image. The data can be converted and displayed as an image using: