Immutability

Following the nested types example:

const person2 = person1.set('givenName', 'Javi')

// person2 is a clone of person1 with the givenName
// set to 'Javi', but person1 is not mutated
person2.fullName() // => 'Javi Cejudo'
person1.fullName() // => 'Javier Cejudo'

const person3 = person1.setIn(['pets', 0, 'name'], 'Bane')

person3.pets().get(0).name() // => 'Bane'
person1.pets().get(0).name() // => 'Robbie'

The same principle applies across all Modélico classes. In the case of M.List, the inner array is frozen. At the time of writing, there is no canonical way of freezing the other inner structures, so a copy is returned each time .inner() is called.

person1.pets().inner().shift().speak()
// => TypeError: Cannot add/remove sealed array elements