> What library? What framework? I lost here. What's effect? There are various libraries that export a function called effect which allows you to run arbitrary

> What library? What framework? I lost here. What's effect? There are various libraries that export a function called effect which allows you to run arbitrary code in response to a signal update. The Preact docs have a great primer on signals and effects: https://preactjs.com/guide/v10/signals#effectfn https://preactjs.com/guide/v10/signals#effectfn As I understand it, these effect functions run the callback once initially to see which signals were accessed while the callback was executing, and then call the callback again whenever the signals it depends on update. As long as signal access is synchronous and single-threaded, you know that if a signal was accessed during the callback's execution that the callback should be subscribed to those signals. > How does effect knows that it needs to call this lambda whenever parity gets changed? Will it call this lambda on any signal change? You can do this with getters [1], where the effect function tracks which properties of the signal were accessed in a getter method (I believe Vue historically did this in version 2), but you can also track object access using proxies [2]. The example from the proposal simply has a 'get' method that is called to access the value of the signal, and executing this method allows dependencies to be tracked. [1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/get https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... [2] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...