CODEWITHSUNDEEP
javascriptarrays
Igor Kim
Igor Kim

Reputation: 77

transform array with objects

Okay, I have 2 arrays:

var state = {
  users: [
    {id: 1, name: 'Igor'},
    {id: 2, name: 'Anton'},
    {id: 3, name: 'Vasya'},
    {id: 4, name: 'Pete'},
    {id: 5, name: 'Dan'}
  ],

  chats: [
    {id: 1, users: [1,2], owner: 1},
    {id: 2, users: [1,2,3], owner: 2},
    {id: 3, users: [3,4,5], owner: 5}
  ]
}

I need a function that returns array like 'chats' but with actual names, not ids. So far I got this:

function loadChats() {
  return state.chats.map(item =>
      ({
        id: item.id,
        users: item.users.map(user => 
          state.users.find(usr => 
            usr.id === user).name),
        owner: item.owner       
      })
    )
}

But I donk think that solution is good, because we dont need to map all the array, just 'users' in it. So can anybody suggest better solution? I was thinking to do smth like this:

...  
state.chats.forEach(item =>
  item.users.map(user => 
    state.users.find(usr => 
      usr.id === user)
  )
)
...

But I don't like using forEach, is there any better solution?

Upvotes: 0

Views: 45

Answers (2)

Shanoor
Shanoor

Reputation: 13692

You're using arrow function so I guess you can use [].find():

var state = {
    users: [
        { id: 1, name: 'Igor' },
        { id: 2, name: 'Anton' },
        { id: 3, name: 'Vasya' },
        { id: 4, name: 'Pete' },
        { id: 5, name: 'Dan' }
    ],

    chats: [
        { id: 1, users: [1, 2], owner: 1 },
        { id: 2, users: [1, 2, 3], owner: 2 },
        { id: 3, users: [3, 4, 5], owner: 5 }
    ]
};

var users = state.users;
var chats = state.chats;

chats = chats.map(function each(chat) {
    // this replace the chat.users array and doesn't touch or hard code any other property
    chat.users = chat.users.map(function (id) {
        return users.find(function (user) {
            return user.id == id;
        }).name;
    });

    return chat;
});

console.log(chats);
document.write('<pre>' + JSON.stringify(chats, null, 3) + '</pre>');

Upvotes: 0

Shilly
Shilly

Reputation: 8589

You're probably better off reducing the user array first and then directly referencing people by id, so you only loop over the users array once. It's no use to find the user in the array for every chat.

var users = state.users.reduce(function ( map, account ) {
        map[account.id] = account.name;
        return map;
    }, {}),
    conversations = state.chats.map(function ( chat ) {
        return {
            'id' : chat.id,
            'users' : chat.users.map(function ( id ) {
                return users[id];
            }),
            'owner' : users[chat.owner]
        };
    });

Upvotes: 2

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