Life & fun · December 19, 2025
LazyPromise = Observable – Signals
A Promise-like primitive which is lazy/cancelable, has typed errors, and emits synchronously instead of on the microtask queue. In a way LazyPromise is what you get if you take an Observable and make it impossible to misuse it for what the Signals were built to do.
LazyPromise = Observable – Signals launched on December 19, 2025 with 34 votes, #492 of 11,628 launches that month and more than 90% of that year's launches.
In plain words
LazyPromise is a Promise-like primitive that operates lazily and can be canceled, with support for typed errors and synchronous emission rather than microtask queue delays. It combines Observable patterns with safeguards to prevent misuse in scenarios where Signals would be more appropriate. The tool is designed for developers who need more control over asynchronous operation timing and error handling than standard Promises provide.
written from the facts on this page · September 2026
From the sources
A tiny alternative to Effect. Contribute to lazy-promise/lazy-promise development by creating an account on GitHub.
Does a similar job
all alternatives →
Cancelable async primitives for JavaScript2017 · github.com · ▲84Composable async primitives with cancelation, control over scheduling, and coroutines. Superior replacement for JS Promises. - mitranim/posterus
A tiny and fast reactive observables library via functions2022 · github.com · ▲72A tiny (~1kB minzipped) and extremely fast library for creating reactive observables via functions. - maverick-js/signals
Lfi – a lazy functional sync, async, and concurrent iteration library2024 · lfi.dev · ▲98Hey HN! Roughly 4 years ago I started building a lazy functional iteration library for JS/TS. I had a few goals for the library: - Supporting sync, sequential async, and concurrent async iteration - Limiting it to a small number of orthogonal concepts that compose beautifully to solve problems - Making it fully tree-shakeable I built it for myself and have (mostly) been its only user as I refined it. I've used it in lots of personal projects and really enjoyed it. I recently decided it would be nice to spread that enjoyment so I created a documentation website complete with a playground…
LazyCode – C++14 composable, lazily evaluated map, filter, fold2018 · github.com · ▲66C++14: bringing in those expressions that you wish you had, Lazily evaluated, compossible generators, maps, filters, ranges and more... - GitHub - SaadAttieh/lazyCode: C++14: bringing in those expressions that you wish you had, Lazily evaluated, compossible generators, maps, filters, ranges and more
LazyVim for Ambitious Developers2024 · lazyvim-ambitious-devs.phillips.codes · ▲68With zero AI generated content. ;-)
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