TypeScript icon, indicating that this package has built-in type declarations

    3.1.5 • Public • Published


    npm version npm downloads Twitter Follow

    This project is part of the @thi.ng/umbrella monorepo.


    Transducer based UI updater for @thi.ng/hdom. This is a support package for @thi.ng/transducers.

    This package provides a single updateDOM function, a side-effecting & stateful transducer which receives @thi.ng/hdom component trees, diffs each against the previous value and applies any required changes to the browser DOM, starting at given root element. By default, incoming values are first normalized using @thi.ng/hdom's normalizeTree() function. See hdom's start() function for more details.

    If the hydrate option is given, the first received tree is only used to inject event listeners and initialize components with lifecycle init() methods and expects an otherwise identical pre-existing DOM. All succeeding trees are diffed then as usual.

    This transducer is primarily intended for @thi.ng/rstream-based dataflow graphs, where it can be used as final leaf subscription / stream transformer to reflect UI changes back to the user, without using the usual RAF update loop used by @thi.ng/hdom by default. In this setup, DOM updates will only be performed if the stream this transducer is attached to receives new values (i.e. hdom component trees).

    Please also see the following hdom references for further details:


    STABLE - used in production

    Search or submit any issues for this package

    Related packages

    • @thi.ng/hdom - Lightweight vanilla ES6 UI component trees with customizable branch-local behaviors
    • @thi.ng/interceptors - Interceptor based event bus, side effect & immutable state handling
    • @thi.ng/rstream - Reactive streams & subscription primitives for constructing dataflow graphs / pipelines


    yarn add @thi.ng/transducers-hdom

    ES module import:

    <script type="module" src="https://cdn.skypack.dev/@thi.ng/transducers-hdom"></script>

    Skypack documentation

    For Node.js REPL:

    # with flag only for < v16
    node --experimental-repl-await
    > const transducersHdom = await import("@thi.ng/transducers-hdom");

    Package sizes (gzipped, pre-treeshake): ESM: 305 bytes


    Usage examples

    Several demos in this repo's /examples directory are using this package.

    A selection:

    Screenshot Description Live demo Source
    Interactive image processing (adaptive threshold) Demo Source
    Figlet-style bitmap font creation with transducers Demo Source
    Canvas based dial widget Demo Source
    Basic crypto-currency candle chart with multiple moving averages plots Demo Source
    Interactive inverse FFT toy synth Demo Source
    Doodle w/ K-nearest neighbor search result visualization Demo Source
    Mouse gesture / stroke analysis, simplification, corner detection Demo Source
    Interactive pattern drawing demo using transducers Demo Source
    Various hdom-canvas shape drawing examples & SVG conversion / export Demo Source
    Isolated, component-local DOM updates Demo Source
    Canvas based Immediate Mode GUI components Demo Source
    Worker based, interactive Mandelbrot visualization Demo Source
    Minimal Markdown to Hiccup to HTML parser / transformer Demo Source
    Basic rstream-gestures multi-touch demo Demo Source
    Polygon to cubic curve conversion & visualization Demo Source
    Animated Voronoi diagram, cubic splines & SVG download Demo Source
    Minimal demo of using rstream constructs to form an interceptor-style event loop Demo Source
    rstream based UI updates & state handling Demo Source
    rstream based spreadsheet w/ S-expression formula DSL Demo Source
    hdom based slide deck viewer & slides from my ClojureX 2018 keynote Demo Source
    Transducer & rstream based hdom UI updates Demo Source


    Generated API docs

    Code for the above linked transducers-hdom example...

    import * as rs from "@thi.ng/rstream";
    import * as tx from "@thi.ng/transducers";
    import { updateDOM } from "@thi.ng/transducers-hdom";
    // root component function
    const app = ({ ticks, clicks }) =>
            `${ticks} ticks and `,
                { href: "#", onclick: () => clickStream.next(0) },
                `${clicks} clicks`]
    // click stream (click counter)
    const clickStream = new rs.Stream().transform(tx.scan(tx.count(-1)));
    // stream combinator
        src: {
            ticks: rs.fromInterval(1000),
            clicks: clickStream,
        reset: false,
        // transform into hdom component
        // apply as DOM
        updateDOM({ root: document.body })
    // kick off


    Karsten Schmidt

    If this project contributes to an academic publication, please cite it as:

      title = "@thi.ng/transducers-hdom",
      author = "Karsten Schmidt",
      note = "https://thi.ng/transducers-hdom",
      year = 2018


    © 2018 - 2021 Karsten Schmidt // Apache Software License 2.0


    npm i @thi.ng/transducers-hdom

    DownloadsWeekly Downloads






    Unpacked Size

    38.6 kB

    Total Files


    Last publish


    • thi.ng