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    1.1.0 • Public • Published


    Relax is a minimal, powerful declarative VDOM and reactive programming library.


    just relax 😌

    This tiny 2.5KB (.min.gz) engine lets you define data-driven apps using declarative components. Relax combines ideas from Meteor, Mithril and Preact into one simple library. Relax supports:

    • Sideways reactive data between components done right
      • reactive computations
      • reactive variables
      • reactive providers
    • Managed diffs (take imperative control when automatic diffs are too expensive)
      • rebasing work (add or override work in a diff)
      • coherent batched updates
      • decoherent time-sliced updates (incremental rendering)
    • Fragments and array return values from render
    • Fibers for efficiently tracking work that is being redone
    • Scheduling (async and sync)
    • Keyed JSX (e.g. <li key="key1">) for efficient diffing
    • Lifecycle methods/hooks
    • Memoization as a replacement for shouldComponentUpdate
    • Rendering-agnostic apps
      • render apps to arbitrary targets (not just the DOM)
    • Well-established DAG algorithms to ensure updates remain efficient (O(n)) and correct
      • stack-safe
      • atomic, solves the "diamond problem" (no redundant renders)

    Relax gives you what you need to build not only simple todo apps, but also rapidly-updating apps like stock tickers.

    FAQs 🤔

    1. Is JSX necessary? No.
    2. Is Relax a view library? Yes. You can code a declarative tree and use a DOM-rendering plugin to render it to the DOM, or a String-rendering plugin to render it to HTML.
    3. Is Relax a state management library? Yes. Relax's state management primitives are powerful enough that you could implement your own MOBX/Redux/Meteor.Tracker.autorun in a few lines of code on top of Relax.
    4. Do I need Redux or MOBX? No. Relax's reactive primitives are sufficient for all apps.
    5. Do I need something like React hooks? No. Sufficient lifecycle methods are provided. If you prefer hooks (closures), you could implement React hooks on top of Relax's lifecycle methods in a few lines of code.
    6. Do updates cause the whole app to re-render? No. Updates scale linearly with the radius of the update, not with the total graph size. If an update only affects 5 nodes, then only those 5 nodes will get their render called.
    7. Do re-renders always update the DOM? No. Mutations are calculated with a keyed diffing algorithm to limit interactions with the DOM. Plugins (DOM Renderer, SSR Renderer, etc.) don't have to think -- Relax "tells plugins what to do".
    8. Are there docs and demos I can read? Soon. I'm currently working on all of that stuff.

    build your own X

    Relax isn't a "framework", it's a small library that helps you avoid huge frameworks. Relax abstracts out the heavy lifting associated with common UI and state management tasks (reconciliation, efficient data flow propagation, reactive functions, etc.). Build your own framework: Many frameworks can be built in a few lines of code with Relax's primitives:

    Relax's inner-diff (instance-level diff) API is inspired by Mithril's redraw. If you prefer React syntax, hooks and other React-like APIs can also be built pretty easily with Relax's primitives:

    • setState
    • functional setState
    • useEffect
    • useLayoutEffect
    • useState
    • useRef
    • Sky is the limit: afterAll, after, before, beforeAll, afterMount, beforeUnmount, afterUpdate

    If you've ever tinkered with Meteor, you've probably been obsessed with Tracker.autorun at some point. Nobody blames you -- it is awesome. If you wanted to, you could implement the exact same API using Relax nodes as Relax supports dependency graphs out-of-the-box. Relax makes it easy to implement reactive patterns such as:

    • Meteor.Tracker
    • Meteor.ReactiveVar
    • Meteor.ReactiveDict
    • Meteor.Collection (reactive collection)
    • Efficient Meteor.Collection.find that supports sort, filter, and multiple listeners per query


    npm install --save atlas-relax

    You are assumed to be familiar with transpiling code (babel, webpack, etc.). In the future, I may make a dist/ folder containing various transpiled-minified code for quick installment.


    Relax is an experimental library and your feedback is greatly appreciated! If Relax has piqued your interest 👀 then read the source code! I've included implementation comments for your reference. If you are curious how some things were implemented, check out the development history. There are a few things I want to implement in the future:

    1. Make plugins agnostic to reducible nodes (makes DOM rendering more efficient)
    2. Error boundaries -- they're useful for larger apps.
      • not as easy to implement as in React, since we may generalize it to DAGs
    3. Ensure DOM renderers can properly hydrate an existing tree to decrease time-to-mount
    4. Docs, demos and examples
    5. Re-roll code into modules, provide optimized dist/ files
      • Use rollup, babel and terser to generate ready-to-use distribution payloads
    6. Reverse queued managed mounts so they mount in expected order.

    inspired by 💜

    Meteor, Mithril, Preact and physics analogies. MIT License.

    The gif above was made with the help of Paul Falstad's atomic dipole transition applet. Check out his other amazing interactive physics playgrounds over at his website:


    npm i atlas-relax

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