Mastering Immutable.js

Setting list values

When you set list values using the set() method, you're changing an existing value. More specifically, you're overwriting the current value at a given index with a new value:

const myList = List.of(1);const myChangedList = myList.set(0, 2);console.log('myList', myList.toJS());// -> myList [ 1 ]console.log('myChangedList', myChangedList.toJS());// -> myChangedList [ 2 ]

You're updating the first list value—because the index you're passing to set() is 0—with a value of 2. Using set() like this is a good choice when you know ahead of time what the new value should be. But what about when the new value depends on the current value?