sveltio

State management solution for Svelte using proxies. Powered by valtio.

Installation

pnpm add valtio sveltio

Usage

// store.ts
import { proxy } from 'sveltio'

export const state = proxy({ count: 0 })

Read from snapshots, mutate the source.

<script lang="ts">
  import { useSnapshot } from 'sveltio'
  import { state } from './store'
  const snap = useSnapshot(state)
</script>

<button on:click={() => state.count++}>
  Clicks: {$snap.count}
</button>

Utilities

derive

You can subscribe to some proxies and create a derived proxy.

import { derive } from 'sveltio/utils'

// create a base proxy
const state = proxy({
  count: 1,
})

// create a derived proxy
const derived = derive({
  doubled: get => get(state).count * 2,
})

// alternatively, attach derived properties to an existing proxy
derive(
  {
    tripled: get => get(state).count * 3,
  },
  {
    proxy: state,
  },
)

proxyWithComputed

You can define own computed properties within a proxy. By combining with a memoization library such as proxy-memoize, optimizing function calls is possible.

import memoize from 'proxy-memoize'
import { proxyWithComputed } from 'sveltio/utils'

const state = proxyWithComputed(
  {
    count: 1,
  },
  {
    doubled: memoize(snap => snap.count * 2),
  },
)

// Computed values accept custom setters too:
const state2 = proxyWithComputed(
  {
    firstName: 'Alec',
    lastName: 'Baldwin',
  },
  {
    fullName: {
      get: memoize(snap => `${snap.firstName} ${snap.lastName}`),
      set: (state, newValue) => {
        [state.firstName, state.lastName] = newValue.split(' ')
      },
    },
  },
)

// if you want a computed value to derive from another computed, you must declare the dependency first:
const state = proxyWithComputed(
  {
    count: 1,
  },
  {
    doubled: memoize(snap => snap.count * 2),
    quadrupled: memoize(snap => snap.doubled * 2),
  },
)

When to use derive over proxyWithComputed?

proxyWithHistory

This is a utility function to create a proxy with snapshot history.

import { proxyWithHistory } from 'sveltio/utils'

const state = proxyWithHistory({ count: 0 })
console.log(state.value) // ---> { count: 0 }
state.value.count += 1
console.log(state.value) // ---> { count: 1 }
state.undo()
console.log(state.value) // ---> { count: 0 }
state.redo()
console.log(state.value) // ---> { count: 1 }

License

MIT