Problem when comparing JavaScript objects in an array

Question

I have these 2 arrays of information. I want to resolve this problem: (Given the name of an user and a required permission, return true if the user have that permission and false otherwise.)

const groups = [
  {
    id: 1,
    name: 'admins',
    permissions: ['CREATE', 'DELETE', 'READ', 'WRITE'],
  },
  {
    id: 2,
    name: 'readers',
    permissions: ['READ'],
  },
  {
    id: 3,
    name: 'writers',
    permissions: ['WRITE'],
  },
  {
    id: 4,
    name: 'managers',
    permissions: ['CREATE', 'DELETE'],
  }
];

const users = [
  {
    name: 'john',
    groups: [1],
  },
  {
    name: 'mary',
    groups: [2, 3],
  },
  {
    name: 'alice',
    groups: [2]
  },
  {
    name: 'bob',
    groups: [3],
  },
  {
    name: 'eve',
    groups: [2, 4],
  },
];

the code I've written so far:

function userHasPermission(userName, requiredPermission) {
  //looping through first array
  for (i = 0; i < users.length; i++) {

    if (users[i].name === userName) {
        // looping through the second array
        for (j = 0; j < groups.length; j++) {

            //here I don't know how to resolve this comparison, because as far as I understand it, the script has to check if userName is a valid ID inside groups array?
            if (users[i].groups.includes(groups[j].id) && (groups[j].permissions.includes(requiredPermission))) {
                return true;
            } else {
                return false;
            }
        }
    }
  }  
  
};

  userHasPermission("mary", "WRITE");

I'm new to Vanilla JavaScript and I'm stuck at this point, any help will be appreciated!

can you post the output also?

vsrukshan
– vsrukshan

2020-11-25 16:07:18 +00:00
Commented Nov 25, 2020 at 16:07 — vsrukshan
– vsrukshan, Commented Nov 25, 2020 at 16:07

hackape · Accepted Answer · 2020-11-25 16:20:36Z

3

function userHasPermission(userName, requiredPermission) {
  //looping through first array
  for (i = 0; i < users.length; i++) {

    if (users[i].name === userName) {
        // looping through the second array
        for (j = 0; j < groups.length; j++) {
            if (users[i].groups.includes(groups[j].id) && (groups[j].permissions.includes(requiredPermission))) {
                return true;
            } else {
                continue;  // don’t return false yet. 
            }
        }
    }
  }  
  // only when you’ve checked all possibilities
  // still find no match, now you can return definitely
  return false;
};

Above is imperative for-loop style based on your code. I personally prefer more functional code style. For your reference:

function userHasPermission(userName, requiredPermission) {
  const targetUser = users.find(user => user.name === userName);
  if (!targetUser) return false;
  
  const userGroups = groups.filter(g => targetUser.groups.includes(g.id));
  const permissions = userGroups.flatMap(g => g.permissions);
  
  return permissions.includes(requiredPermission);
}

edited Nov 25, 2020 at 16:20

answered Nov 25, 2020 at 16:10

hackape

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1 Comment

hackape Over a year ago

Off topic, but I can’t help to add, the permissions field of group object don’t have to be an array of string. If you have control over the code, try look into using bit masks for access control

Brendon · Accepted Answer · 2020-11-25 16:22:20Z

1

function userHasPermission(userName, requiredPermission) {
     const user = users.find(u => u.name === userName);
     let result = false;

     user.groups.forEach(id => {
        const group = groups.find(g => g.id === id);
        result = group.permissions.includes(requiredPermission);
     });

     return result;
};

userHasPermission("mary", "WRITE");

answered Nov 25, 2020 at 16:22

Brendon

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