6

I am working with the Loopback Framework, doing a web project. But I think that the question that I am exposing here has less to do with this, but with general Javascript / Node.JS knowledge.

At one part of the code, I am doing:

roleMapping.find({
        where: {
            principalType: 'USER',
            principalId: context.principals[0].id
        },
        include: 'role'
    }, function(err, roles){
        console.log(roles[0]);
        for (var i in roles)
        {
            if (roles[i].role.name === 'teamLeader' &&
                roles[i].groupId === context.modelId)
            {
                cb(null,true);
            }else {
                cb(null,false);
            }
        }
});

Ok with this, but it fails when trying to compare roles[i].role.name. So, I went logging what the roles[i] object contained.

    { groupId: 1,
  id: 3,
  principalType: 'USER',
  principalId: 1,
  roleId: 2,
  role: 
   { id: 2,
     name: 'teamLeader',
     description: 'The leader(s) of a team',
     created: null,
     modified: null } }

Ok, nothing wrong, but it still fails, so I tried to print just the role property. And to my surprise:

{ [Function]
  update: [Function],
  destroy: [Function],
  create: [Function],
  build: [Function],
  _targetClass: 'Role' }

So, the role property seems to be some sort of function? But how it was been correctly printed before?

Eventually, lost in my frustration I tried var role = JSON.parse(JSON.stringify(roles[i]));

And then I could access every property of the object normally, but this is not clean nor normal.

This blew my mind for the first time in years of JS programming (sort of amateurish though), and I would be pleased if someone could clarify this to me. Thanks

EDIT: It seems that it is specific to this Framework, so I'm changing title to help community.

Dark_eye
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  • Can you show us the code you used to print them? – Bergi Jun 18 '15 at 22:58
  • `console.log(roles[i]);` printing whole object ok, and `console.log(roles[i].role)` printing the weird thing. – Dark_eye Jun 18 '15 at 23:01
  • I think I've seen mongodb doing similar weird things. Does `roles[i]` have a `.toJSON` method? – Bergi Jun 18 '15 at 23:15
  • Yeah it looks like you need to extract the actual value (your object) somehow. It also looks like the logged object might in fact be a function. Does `roles[i]()` return anything? – Jan Jun 18 '15 at 23:19
  • Thay may have something to do with the behaviour of the `for (... in ...)` loop. You could try using `for (var i = 0, length = roles.length; i < length; i++) { }` instead. See https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/for...in – reg4in Jun 18 '15 at 23:20
  • Yes it does! `roles[i].toJSON()` prints the same as the first `console.log(roles[i]);` But it's no MongoDB, I am using MySQL as the data backend, but maybe Loopback is trying to emulate some MongoDB? – Dark_eye Jun 18 '15 at 23:20
  • @Jan no, it crashes with `Object [object Object] has no method '0'` – Dark_eye Jun 18 '15 at 23:24
  • would like to link this question to [this answer](https://stackoverflow.com/a/51226178/1870331) too. – Gagan Oct 29 '18 at 10:09

1 Answers1

10

I just found issue 1425 which links to the following docs:

With Node.js API, you need to call toJSON() to convert the returned model instance with related items into a plain JSON object

Please note the relation properties […] points to a JavaScript function for the relation method.

So it seems you have to use

for (var i=0; i<roles.length; i++) {
    var x = roles[i].toJSON();
    cb(null, x.role.name === 'teamLeader'
             && x.groupId === context.modelId);
}
Bergi
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