Understanding how Jotai works to store atom values

So far, we haven't discussed how Jotai uses Context. In this section, we'll show how Jotai stores atom values and how atoms are reusable.

First, let's revisit a simple atom definition, countAtom. atom takes an initial value of 0 and returns an atom config, as follows:

const countAtom = atom(0);

Implementation-wise, countAtom is an object holding some properties representing the atom behavior. In this case, countAtom is a primitive atom, which is an atom with a value that can be updated with a value or an updating function. A primitive atom is designed to behave like useState.

What is important is that atom configs such as countAtom don't hold their values. We have a store that holds atom values. A store has a WeakMap object whose key is an atom config object and whose value is an atom value.

When we use useAtom, by default, it uses a default store defined at the module level. However, Jotai provides...