immutable.js map over array (List) and add a property

Question

I'm just starting with immutable.js and I'm having trouble figuring out how to set a new property on objects within an array. I'm having trouble finding any examples in the docs of this kind of change.

I'm basically just trying to take change this:

[{ 
  gitInfo: {id: 8001, host: '', …},
  module: {id: 24875, name: "blah", …}
}...]

to this:

[{ 
  gitInfo: {id: 8001, host: '', …},
  module: {id: 24875, name: "blah", isStared: true …}
}...]

So w/out immutable.js I would have something like:

function markModules(modules) {
    modules.map( (module) => {
      module.module.isStarred = false;
      if (contains(this.props.stars, module.module.id)) {
        module.module.isStarred = true;
      }
    })
    return modules;
  }

I'm assuming I need something like set() with a List, but again, I'm not finding any examples how to do this.

Thanks for any tips or links to examples.

Luqmaan · Accepted Answer · 2015-11-28 01:24:09Z

You'd do it the same way you would without Immutable.js (.map).

const data = Immutable.fromJS([{ 
  gitInfo: {id: 8001, host: ''},
  module: {id: 24875, name: "blah"}
}, { 
  gitInfo: {id: 6996, host: ''},
  module: {id: 666, name: "wef"}
}]);

const transformed = data.map((x) => {
    return x.get('module').set('isStarred', true);
})

transformed.toJS() === [
  {
    "id": 24875,
    "name": "blah",
    "isStarred": true
  },
  {
    "id": 666,
    "name": "wef",
    "isStarred": true
  }
]

And if you want to put the extra logic in there:

function markModules(modules) {
  return modules.map((module) => {
    const isStarred = contains(this.props.stars, module.getIn(['module', 'id']));
    return module.setIn(['module', 'isStarred'], isStarred);
  })
}

The key is to turn your if statements into values/functions that return values instead of updating the data structure.

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