Add data to nested object using dynamic keys

Question

I have an empty object structured like so :

let users = {
  "type1": {
      "group1": {
          "role1": {}
      },
      "group2": {
          "role2": {},
          "role3": {},
          "role4": {}
      },
  },
  "type2": {
      "group1": {
          "role1": {}
      },
      "group2": {
          "role2": {}
      },
      "group3": {
          "role3": {},
          "role4": {}
      }
  }
};

I am then fetching my users with an associated type, group and role for each one. I would like to dynamically add my users to my object above in the right type/group/role combination as they are stored in variables.

I tried something like this but this is wrong:

fetchedUsers.forEach(user => {
  users[user.type][user.group][user.role].push(user.email);
})

Is there a way to do this similar to what I tried ?

Those roles are (empty) objects. You can't push something into an object, only an array since push is an array method. — Andy
– Andy, Commented May 12, 2022 at 13:18
The closest analog to Array#push is Object.assign though it doesn't modify the target object in place, so you will still need to do some reconstructive work. — D M
– D M, Commented May 12, 2022 at 13:20
I know I can't I am searching for the closest way to do this but with an object @Andy — Ryan
– Ryan, Commented May 12, 2022 at 13:27
I was just pointing out why your code doesn't work. It would help to see what your expect your updated object should look like. Should a role look like this: role: { name: 'Bob', role: 'admin' } where there is only one role assigned to it, or role: [{ name: 'Bob', role: 'admin'}, { name: 'Jo', role: 'user' }] where there are many roles assigned to an array. How you want your output to look depends solely on what that structure is meant to look like. @Ryan — Andy
– Andy, Commented May 12, 2022 at 13:40
@Ryan I added a version with one email per role, keyed emails and an array of emails — mplungjan
– mplungjan, Commented May 12, 2022 at 14:09

mplungjan · Accepted Answer · 2022-05-12 14:05:39Z

You cannot push to an object. Your role is not an array

let users = { 
"type1": { "group1": { "role1": {} },
           "group2": { "role2": {}, "role3": {}, "role4": {}},},
"type2": { "group1": { "role1": {} },
           "group2": { "role2": {}},
           "group3": { "role3": {}, "role4": {}}}};

const fetchedUsers = [
  {"type":"type1","group": "group2", "role":"role3", "email":"[email protected]"},
  {"type":"type2","group": "group1", "role":"role1", "email":"[email protected]"}
];

fetchedUsers.forEach(
  ({type,group,role,email}) => users[type][group][role].email = email
);
console.log(users)

If you have more than one email per role, you need to make some keys

let users = { 
"type1": { "group1": { "role1": {} },
           "group2": { "role2": {}, "role3": {}, "role4": {}},},
"type2": { "group1": { "role1": {} },
           "group2": { "role2": {}},
           "group3": { "role3": {}, "role4": {}}}};

const fetchedUsers = [
  {"type":"type1","group": "group2", "role":"role3", "email":"[email protected]"},
  {"type":"type2","group": "group1", "role":"role1", "email":"[email protected]"},
  {"type":"type2","group": "group1", "role":"role1", "email":"[email protected]"}
];

fetchedUsers.forEach(
  ({type,group,role,email}) => {
    const currentRole = users[type][group][role]
    const len = Object.entries(currentRole).length
    currentRole[`email${len}`] = email
});
console.log(users)

or use an array

let users = { 
"type1": { "group1": { "role1": {} },
           "group2": { "role2": {}, "role3": {}, "role4": {}},},
"type2": { "group1": { "role1": {} },
           "group2": { "role2": {}},
           "group3": { "role3": {}, "role4": {}}}};

const fetchedUsers = [
  {"type":"type1","group": "group2", "role":"role3", "email":"[email protected]"},
  {"type":"type2","group": "group1", "role":"role1", "email":"[email protected]"},
  {"type":"type2","group": "group1", "role":"role1", "email":"[email protected]"}
];

fetchedUsers.forEach(
  ({type,group,role,email}) => {
    const currentRole = users[type][group][role]
    currentRole.emails = currentRole.emails || []
    currentRole.emails.push(email)
});
console.log(users)

Taki · Accepted Answer · 2022-05-12 13:27:12Z

2

Since users[user.type][user.group][user.role] is an object you can't use push()

If you initialise the empty role structures as arrays it should work.

let users = {
  "type1": {
      "group1": {
          "role1": []
      },
      "group2": {
          "role2": [],
          "role3": [],
          "role4": []
      },
  },
  "type2": {
      "group1": {
          "role1": []
      },
      "group2": {
          "role2": []
      },
      "group3": {
          "role3": [],
          "role4": []
      }
  }
};

answered May 12, 2022 at 13:27

Taki

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3 Comments

Ryan Over a year ago

This works well indeed, but I also need a way to keep roles as an object unhappily...

Taki Over a year ago

Alright. Then I'd probably do something like users[user.type][user.group][user.role][user.email] = user.email this will sett each row in a role like {[email protected]: '[email protected]', [email protected]: '[email protected]'} etc.

Ryan Over a year ago

Alright yes thank you this works as I wanted !

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