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• About
• Status
• Related packages
• Installation
• Dependencies
• Usage examples
• API
• Authors
• License

About

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:

• start()
• HDOMOpts

Status

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

Installation

yarn add @thi.ng/transducers-hdom

ESM import:

import * as th from "@thi.ng/transducers-hdom";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/transducers-hdom"></script>

JSDelivr documentation

For Node.js REPL:

const th = await import("@thi.ng/transducers-hdom");

Package sizes (brotli'd, pre-treeshake): ESM: 272 bytes

Dependencies

• @thi.ng/hdom
• @thi.ng/hiccup
• @thi.ng/transducers

Usage examples

21 projects in this repo's /examples directory are using this package:

| Screenshot | Description | Live demo | Source | |:-------------------------------------------------------------------------------------------------------------------------------------|:---------------------------------------------------------------------------------|:----------------------------------------------------------|:---------------------------------------------------------------------------------------| | | Interactive image processing (adaptive threshold) | 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 | | | K-nearest neighbor search in an hash grid | 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 | | | 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 |

API

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 }) =>
    ["div",
        `${ticks} ticks and `,
        ["a",
            { href: "#", onclick: () => clickStream.next(0) },
            `${clicks} clicks`]
    ];

// click stream (click counter)
const clickStream = new rs.Stream().transform(tx.scan(tx.count(-1)));

// stream combinator
rs.sync({
    src: {
        ticks: rs.fromInterval(1000),
        clicks: clickStream,
    },
    reset: false,
}).transform(
    // transform into hdom component
    tx.map(app),
    // apply as DOM
    updateDOM({ root: document.body })
);

// kick off
clickStream.next(0);

Authors

• Karsten Schmidt

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

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

License

© 2018 - 2025 Karsten Schmidt // Apache License 2.0