Usage

Hotlink it from https://unpkg.com/valoo.

See Interactive Codepen Demo.

import valoo from 'https://unpkg.com/valoo'

// create an observable value:
const num = valoo(42)

// subscribe to value changes:
const off = num.on( v => console.log(v) )

// unsubscribe that listener:
off()

// set the value, invoking any listeners:
num(43)

// get the current value:
num()  // 43

Other Versions

• valoo-lite.mjs: lighter 120b version, but doesn't support unsubscribing.
• valoo-original.mjs: v1-compatible, with subscribe handled via overloading.

Credit

The idea here was first implemented in Mithril. I believe the subscription mechanism is new though.

License

Apache-2.0. Copyright 2018 Google LLC.