@maastrich/atoms

@maastrich/atoms is an alternative to react Contexts that is expensive in performance.

Installation

npm install @maastrich/atoms

or

yarn add @maastrich/atoms

Usage

useAtom

import { useAtom } from "@maastrich/atoms";

function MyComponent() {
  /*
   * Creates an atom with id "MyComponent.simple" if it doesn't exist yet with a default value of "initial value".
   * If the atom already exists (created by a parent component of an earlier render of this component),
   * the default value provided will be ignored.
   *
   * The defaultValue is optional.
   *
   * simpleAtom contains the current value of the atom.
   * setSimpleAtom is a function that can be used to update the value of the atom.
   * clearSimpleAtom is a function that can be use to delete the atom, you can use when the component is unmounted.
   *
   * Note: The atom is not persisted between renders if you do not clear it.
   */
  const [simpleAtom, setSimpleAtom, clearSimpleAtom] = useAtom(
    "MyComponent.simple",
    "initial value"
  );

  /*
   * Creates an atom with id "MyComponent.complex"
   * If the default value is a callback, the value will be computed from this callback, if the callback returns a promise,
   * the value will be awaited.
   *
   * If the rendering depends on the async callback, a boolean is provided as the fourth element of the array,
   * it will be true when the promise is fulfilled.
   */
  const [asyncAtom, setAsyncAtom, clearAsyncAtom, asyncAtomMounted] = useAtom(
    "MyComponent.async",
    async () => {
      const response = await fetch("https://api.github.com/users/maastrich");
      return response.json();
    }
  );

  if (!asyncAtomMounted) {
    return (
      <div>
        <div>
          <p>{simpleAtom}</p>
          <button onClick={() => setSimpleAtom((prev) => prev + 1)}></button>
        </div>
        <p>Loading asyncAtom...</p>
      </div>
    );
  }
  return (
    <div>
      <div>
        <p>{simpleAtom}</p>
        <button onClick={() => setSimpleAtom((prev) => prev + 1)}></button>
      </div>
      <p>{asyncAtom}</p>
    </div>
  );
}

useAtomValue

useAtomValue has the same prototype as useAtom, but it returns the current value and the mounted attribute of the atom instead of the atom itself. It is useful when you just need to use the value in a child component or so

import { useAtomValue, useAtom } from "@maastrich/atoms";

const [simpleAtom, simpleAtomMounted] = useAtomValue("MyComponent.simple", "initial value");

// is equivalent to

const [simpleAtom, , , simpleAtomMounted] = useAtom("MyComponent.simple", "initial value");

useSetAtom

import { useSetAtom, useAtom } from "@maastrich/atoms";

const setSimpleAtom = useSetAtom("MyComponent.simple");

// is equivalent to

const [, setSimpleAtom] = useAtom("MyComponent.simple");

useClearAtom

import { useClearAtom, useAtom } from "@maastrich/atoms";

const clearSimpleAtom = useSetAtom("MyComponent.simple");

// is equivalent to

const [, , clearSimpleAtom] = useAtom("MyComponent.simple");