Updating one key in list of maps using ImmutableJS

Question

Docs for immutable.js, lack descriptive examples. Could somebody kindly explain, how I could perform the following in ImmutableJS:

function isOdd (v) {
    return v % 2 === 0
}

var collection = [{a: 1, b: 2}, {a: 3, b: 7}, {a: 5, b: 6}];
collection.map(item => {
 if (isOdd(item.b))  {
   item.a = item.a * 2;
 }
 return item;
})

Any help is highly appreciated.

Todd Moore · Accepted Answer · 2016-01-30 00:48:32Z

1

const collection = Immutable.fromJS([{a: 1, b: 2}, {a: 3, b: 7}, {a: 5, b: 6}]);

const isOdd = a => b => b % 2 ? a : a * 2;  

collection
  .map(item => item
      .update('a', a => isOdd(a)(item.get('b'))))

Check the console output of this pen: http://codepen.io/anon/pen/Nxzdwe?editors=1012

edited Jan 30, 2016 at 0:48

answered Jan 29, 2016 at 12:00

Todd Moore

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2 Comments

Dmitry Chirkin Over a year ago

Almost but not. It will return only array of changed values but i want whole collection This answer gave me some ideas with .map

Todd Moore Over a year ago

Didn't realise that was what you wanted, have updated with my suggestion. See the updated codepen

Dmitry Chirkin · Accepted Answer · 2016-01-29 16:01:34Z

0

So here is my version:

const collection = Immutable.fromJS([{a: 1, b: 2}, {a: 3, b: 7}, {a: 5, b: 6}]);

console.log(
  collection    
    .map(item => {
      if (item.get('b') % 2 == 0) {
        return item.set('a', item.get('a') * 2)
      } else {
        return item;
      }
    }).toJS()
);

answered Jan 29, 2016 at 16:01

Dmitry Chirkin

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