Immutable.js has one more tool for creating immutable data in addition to everything we've looked at so far in this chapter. The fromJS() function is similar to a JSON parser, because it parses the same types of JavaScript objects that you'll see when you parse JSON strings: objects and arrays.
You can parse a regular JavaScript array, resulting in a list, as shown here:
import { fromJS } from 'immutable';
const myList = fromJS([1, 2, 3]);
console.log('myList', myList.get(0));
// -> myList 1This is just like passing the array to the List constructor.
You can parse a regular JavaScript object, resulting in a map:
const myMap = fromJS({
one: 1,
two: 2,
three: 3
});
console.log('myMap', myMap.get('one'));
// -> myMap 1Once again, this is just like passing the object literal to the Map constructor.