8.3 Avoiding mutations by updating non-destructively

We can avoid mutations if we only update data non-destructively.

Background

For more information on updating data, see §7 “Updating data destructively and non-destructively”.

8.3.1 How does non-destructive updating help with shared mutable state?

With non-destructive updating, sharing data becomes unproblematic, because we never mutate the shared data. (This only works if everyone that accesses the data does that!)

Intriguingly, copying data becomes trivially simple:

const original = {city: 'Berlin', country: 'Germany'};
const copy = original;

This works, because we are only making non-destructive changes and are therefore copying the data on demand.