svelte-contextify

A tiny library for vastly improving context managament within your Svelte/SvelteKit apps by encapsulating the Context API.

Features

• Removes the need for keys.
• Removes key collisions by using the Symbol API.
• Improves type safety when setting and getting context.
• Improves error handling when retrieving unset context.

Installation

Install through npm using your preferred package manager:

npm i svelte-contextify

pnpm add svelte-contextify

yarn add svelte-contextify

bun add svelte-contextify

API

createContext(options)

See: source

The problem

Let's say we want to share the session of a user in our app through context, one might do that like so:

/** session.ts */

interface Session {
    username: string;
}

export type { Session };

<!-- App.svelte -->

<script lang="ts">
    import Component from '$lib/Component.svelte';
    import { setContext } from 'svelte';
    import type { Session } from '$lib/session.ts';

    setContext<Session>('session', { username: 'Hugos68' });
</script>

<Component />

<!-- Component.svelte -->

<script lang="ts">
    import { getContext } from 'svelte';
    import type { Session } from '$lib/session.ts';

    const session = getContext<Session>('session');
</script>
s
<p>Welcome: {session.username}!</p>

While this approach does work, it is flawed for two reasons:

1. We need to keep track of the context key (session) in atleast two different places.
2. We need to keep track of the Session type in atleast two different places.

How svelte-contextify solves the problem

This library aims to solve the problem by handling the key and type inference for you using the createContext function.

This allows you to refactor the code from above, into:

/** session.ts */

import { createContext } from 'svelte-contextify';

interface Session {
    username: string;
}

const {
    get: getSession,
    set: setSession
} = createContext<Session>({ defaultValue: { username: 'guest' } });

export { getSession, setSession };
export type { Session };

<!-- App.svelte -->

<script lang="ts">
    import Component from '$lib/Component.svelte';
    import { setSession } from '$lib/session.ts';

    setSession({ username: 'Hugos68' });
    //         ^ Type safety when setting context
</script>

<Component />

<!-- Component.svelte -->

<script lang="ts">
    import { getSession } from '$lib/session.ts';

    const session = getSession('session');
    //    ^ Type is inferred as Session
</script>

<p>Welcome: {session.username}!</p>

As you can see this notably improved using context as we now:

• Don't need to define a key at all, which removes the need to keep the keys in sync.
• Only have to pass the type once when creating the context, which removes the need from keeping the types in sync.

License

This project is licensed under the Apache-2.0 License - see the LICENSE file for details.