Node JS [Object Map] while writing object to file

Question

I read many posts on stackoverflow and other tutorial sites for writing object/JSON to a file, but none of the solutions worked for me.

1) Code:

let messages = await fetchMessages()
console.log(messages)    // Prints an object
fs.writeFileSync('./msgdata.json', messages , 'utf-8'); 

2) Also tried,

fs.writeFileSync('./msgdata.json', JSON.stringify(messages) , 'utf-8'); 

3) Also tried,

fs.writeFile(), but get same output as above.

msgdata.json: (For 1)

[object Map]

msgdata.json: (For 2 & 3)

{}

Can someone please point out what could be causing this?

## Output of console.log(messages) ##

OUTPUT contains 10 more such objects having different id's:

channel:
   TextChannel {
     type: 'text',
     id: '424825532274253312',
     name: 'request',
     position: 69,
     parentID: '397363224286473987',
     permissionOverwrites: [Object],
     topic: null,
     nsfw: false,
     lastMessageID: '427143105410760704',
     guild: [Object],
     messages: [Object],
     _typing: Map {} },
  id: '427142596817846272',
  type: 'DEFAULT',
  content: '**Select your emoji:** __***Group 9:***__',
  author:
   ClientUser {
     id: '407083773537350272',
     username: 'Bot',
     discriminator: '9256',
     avatar: '9c374e719ba2ab4e69fd577005b635bf',
     bot: true,
     lastMessageID: null,
     lastMessage: null,
     verified: true,
     email: null,
     localPresence: {},
     _typing: Map {},
     friends: Collection {},
     blocked: Collection {},
     notes: Collection {},
     premium: null,
     mfaEnabled: false,
     mobile: null,
     settings: [Object],
     guildSettings: Collection {} },
  member:
   GuildMember {
     guild: [Object],
     user: [Object],
     _roles: [Array],
     serverDeaf: false,
     serverMute: false,
     selfMute: undefined,
     selfDeaf: undefined,
     voiceSessionID: undefined,
     voiceChannelID: undefined,
     speaking: false,
     nickname: null,
     joinedTimestamp: 1517127343434,
     lastMessageID: null,
     lastMessage: null },
  pinned: false,
  tts: false,
  nonce: undefined,
  system: false,
  embeds: [],
  attachments: Collection {},
  createdTimestamp: 1521909131007,
  editedTimestamp: null,
  reactions:
   Collection {
     'taillow:417281639777959940' => [Object],
     'shroomish:417281639899463680' => [Object],
     'sableye:417281640197521419' => [Object],
     'ralts:417281642735075329' => [Object],
     'sentret:417281644001624076' => [Object],
     'shuppet:417281644291162132' => [Object],
     'torchic:417281647210397706' => [Object],
     'snubbull:417281647692480522' => [Object],
     'sunkern:417281647763783681' => [Object],
     'slowpoke:417281648653107200' => [Object],
     'teddiursa:417281649537974273' => [Object],
     'sneasel:417281649613471747' => [Object],
     'snorunt:417281649819123712' => [Object],
     'surskit:417281650163056640' => [Object],
     'qwilfish:417281654629859348' => [Object],
     'shelgon:417281654730522624' => [Object] },
  mentions:
   MessageMentions {
     everyone: false,
     users: Collection {},
     roles: Collection {},
     _content: '**Select your emoji:** __***Group
9:***__',
     _client: [Object],
     _guild: [Object],
     _members: null,
     _channels: null },
  webhookID: null,
  hit: null,
  _edits: [] },

Answer 1

This is because the object returned is a Map object (MDN). When you JSON.strigify a Map object, it always returns {}. There are two ways to get readable JSON that stores your map. The first is to loop over all the entries and create a JSON (taking in consideration the keys and values). That should be simple to achieve.

Another way is to create an array from the Map and then stringify it.

fs.writeFileSync('./msgdata.json', JSON.stringify([...myObject]) , 'utf-8');