Setting map values

The set() method for maps is used to add and to change collection values. If the key that's being set doesn't exist, then the key-value pair is set for the first time. If the key does exist, then the previous value of that key is replaced with the new value, as follows:

const myMap = Map.of('one', 1);
const myChangedMap = myMap.set('one', 'one');

console.log('myMap', myMap.toJS());
// -> myMap { one: 1 }
console.log('myChangedMap', myChangedMap.toJS());
// -> myChangedMap { one: 'one' }

Calling set() produces a new map, because all Immutable.js mutations are persistent changes.