transform array with objects

Question

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?

Your state object in your example is wrong. users and chats should be assigned using : not =. — An0nC0d3r
– An0nC0d3r, Commented Dec 23, 2015 at 10:21
@Tushar ids wont be numeral and in order, that is just example, they will be random 6-symbol combination — Igor Kim
– Igor Kim, Commented Dec 23, 2015 at 10:26
@ikffs Then you need an object having multiple elements inside it having key as id(unique` and value as username. — Tushar
– Tushar, Commented Dec 23, 2015 at 10:28

Shilly · Accepted Answer · 2015-12-23 10:17:52Z

2

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]
        };
    });

answered Dec 23, 2015 at 10:17

Shilly

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2 Comments

Igor Kim Over a year ago

problem is that ids won't be numeral and in order, it was for example, they will be 6 random symbols

Shilly Over a year ago

Doesn't matter, you're reducing the names into an object, and objects can have any valid string as a key.

Shanoor · Accepted Answer · 2015-12-23 10:32:05Z

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>');

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