Observable state with ease. ⚡️

Bring your React components to the next level. ⚛️

• Transparent proxies (no special classes!)
• Implicit observation (use your objects like normal!)
• Observable arrays, sets, and maps
• Automatic effects
• Small footprint

The entirety of wana is 10 functions:

• o for making observable objects
• auto for reactive effects
• when for reactive promises
• no for unobserved objects
• noto for unobserved scopes
• watch for listening to deep changes
• withAuto for reactive components
• useAuto for easy auto calls in components
• useO for observable component state
• useDerived for observable getters
• useChanges for change listeners

The o function wraps an object with an observable proxy (sorry, no IE11 support). These proxies are transparent, which means they look and act just like the object they wrap. The only difference is that now they're observable!

Even custom class instances can be wrapped with an observable proxy!

Passing the same object into o twice always returns the same proxy.

By wrapping a function with o, you get an observable getter, which memoizes its result until one of its observed values is changed. Calling an observable getter triggers an observation! To prevent leaks, call the dispose method before releasing an observable getter. Lastly, you can call the clear method to force re-memoization on next call.

Passing an observable getter into o is a no-op.

Passing a primitive value into o is a no-op.

Note: Nested objects are not made observable. You'll need to wrap them with o calls too.

import { o } from 'wana'

const state: any[] = o([])
const state = o({ a: 1 })
const state = o(new Set())
const state = o(new Map())

The auto function runs the given effect immediately and tracks which observables are used. Upon changes to any of those observables, auto repeats the same process.

It does its best to react only to changes that affect its outcome.

import { o, auto } from 'wana'

const state = o({ count: 0 })

const observer = auto(() => {
  console.log(state.count % 2 ? 'even' : 'odd')
}) // logs "even"

state.count++ // logs "odd"
state.count++ // logs "even"

// Remember to call "dispose" to stop observing.
observer.dispose()

The auto function accepts a config object:

• onError?: (this: Auto, error: Error) => void
• delay?: number | boolean

When delay === true, reactions are batched using the microtask queue. This is the default behavior.

When delay > 0, reactions are batched using setTimeout.

By default, auto errors are rethrown. When delay <= 0, reactions are synchronous, so the stack trace will show you which observable was changed before the error.

You should always provide an onError callback when delay is true. Otherwise, an unhandled promise rejection is imminent.

auto(effect, {
  delay: true,
  onError(error) {
    // The `run` method lets you replace the effect.
    this.run(newEffect)
  }
})

The when function creates a promise that resolves when the given condition returns true.

Any observable access within the condition is tracked. The condition is rerun whenever a change is detected.

import { o, when } from 'wana'

const obj = o({ count: 0 })
const promise = when(() => obj.count > 1)

obj.count++ // "promise" stays pending
obj.count++ // "promise" is resolved

The promise is rejected when the condition throws an error.

The no function takes any observable object and returns the underlying object that isn't observable.

import { o, auto, no } from 'wana'

const obj = o({ a: 1, b: 2 })
auto(() => {
  // This will only be logged once.
  console.log(no(obj).a + no(obj).b)
})

// This change will not be observed.
obj.a = 2

Pass a function to wrap it with a new function that disables implicit observation for each call.

const state = o({
  count: 1,
})

const increment = no((n: number) => {
  state.count = state.count + n
})

auto(() => {
  increment(1) // Nothing will be observed in here.
})

state.count == 2 // => true

Pass anything else and you get the same value back.

The noto function (pronounced "not oh") is the exact opposite of the auto function. The function you pass to noto is called immediately (with implicit observation disabled) and whatever you return is passed through. Your function is never called again after that.

import { o, auto, noto } from 'noto'

const state = o({ count: 0 })

// Create an auto observer.
auto(() => {
  // Do something you want observed.
  noto(() => {
    // Do something you don't want observed.
  })
})

It's also useful inside methods of an observable object:

const state = o({
  count: 0,
  // Calling "increment" in an observable scope does
  // *not* result in "count" being observed.
  increment() {
    noto(() => this.count++)
  }
})

The watch function lets you listen for deep changes within an observable object.

import { o, watch } from 'wana'

const obj = o({ arr: o([]) })
const observer = watch(obj, change => console.log('changed:', change))

// Every observable object in `obj` is watched.
obj.x = true
obj.arr.push(1)

// You can even add new observables!
const foo = o({})
obj.arr.push(foo)
foo.x = true

// Call "dispose" to stop observing.
observer.dispose()

Note: When an object is made observable after being added to a watched object, it won't be watched. Be sure you pass objects to o() before adding them to a watched object!

The withAuto function wraps a React component, giving it the ability to track which observables are used during render. Upon changes to any of those observables, withAuto re-renders the component.

For convenience, you can add a ref argument to your component, and withAuto will wrap it with React.forwardRef for you. ✨

Note: Class components are not supported.

import { o, withAuto } from 'wana'

const MyView = withAuto(props => (
  <div>{props.user.name}</div>
))

const user = o({ name: 'Alec' })
const view = <MyView user={user} /> // renders "Alec"

user.name = 'Alice' // renders "Alice"

The useAuto hook calls auto within a useEffect callback, allowing you to run an effect in response to observable changes.

import { useAuto } from 'wana'

const MyView = props => {
  useAuto(() => {
    console.log(props.user.name)
  })
  return null
}

const user = o({ name: 'John Lennon' })
const view = <MyView user={user} /> // logs "John Lennon"

user.name = 'Yoko Ono' // logs "Yoko Ono"

The useO hook is very similar to React.useMemo, except the returned object is observable, the deps array is optional, and you can pass an object or a function (instead of only a function).

import { useO } from 'wana'

const MyView = props => {
  const state = useO({ a: 1 })
  const state = useO(new Set(), deps)
  const state = useO(() => [1, 2, 3])
  const state = useO(() => new Map(), deps)
}

When you pass a function that returns a function, you get an observable getter, which is disposed of automatically on dismount. You can even pass a deps array as the last argument if you want to mix non-observable props into the memoized value.

The useDerived hook creates an observable getter. You can pass a deps array as the last argument if you want to mix non-observable props into the memoized value.

import { o, useDerived, useAuto } from 'wana'

const state = o({ count: 0 })

const MyView = props => {
  const foo = useDerived(() => state.count + props.foo, [props.foo])
  useAuto(() => {
    console.log('foo:', foo())
  })
  return <div />
}

The useChanges hook lets you listen for Change events on an observable object. Only shallow changes are reported.

import { o, useChanges } from 'wana'

const state = o({ count: 0 })

const MyView = () => {
  useChanges(state, console.log)
  return null
}

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