Mastering Immutable.js

Accumulating values

Basic arithmetic is another use of reducers. In the preceding section, we looked at minimums and maximums—the reduction is produced by performing comparisons. With accumulators, we're just changing the reduction based on simple addition and other operators. Let's take a look at some basic accumulators:

const myList = List.of(  Map.of('red', 3, 'black', 4),  Map.of('red', 6, 'black', 8),  Map.of('red', 9, 'black', 12));const redSum = myList.reduce(  (result, v) => result + v.get('red'),  0);const blackSum = myList.reduce(  (result, v) => result + v.get('black'),  0);console.log('myList', myList.toJS());// -> myList [ { red: 3, black: 4 },// ->          { red: 6, black: 8 },// ->          { red: 9, black: 12 } ]console.log('redSum', redSum);// -> ...