TermDOM

Build terminal apps with HTML, CSS and the DOM.

TermDOM is a JavaScript library that displays HTML and CSS in the terminal. It draws actual DOM nodes to terminal output and redraws the screen when they mutate, so TUIs and interactive CLIs can be written with vanilla JavaScript or any frontend web framework.

npm install @b9g/termdom

import {TermDOM} from "@b9g/termdom";

const term = new TermDOM();
term.attach();

// The document is a real DOM document.
const {document} = term;
document.body.innerHTML = `
  <style>
    .card { border: 1px solid #5fafff; padding: 0 1ch; width: 36ch; }
    .title { color: #5fafff; font-weight: bold; }
    .done { color: green; }
    .rest { color: #444; }
    .pct { color: #888; }
  </style>
  <div class="card">
    <div class="title">Installing</div>
    <div>
      <span class="done" id="done"></span><span class="rest" id="rest"></span>
      <span class="pct" id="pct"></span>
    </div>
  </div>
`;

// TermDOM observes mutations and re-renders automatically.
let n = 0;
setInterval(() => {
  n = (n + 1) % 101;
  const cells = Math.round(n / 4);
  document.getElementById("done").textContent = "█".repeat(cells);
  document.getElementById("rest").textContent = "░".repeat(25 - cells);
  document.getElementById("pct").textContent = String(n).padStart(3) + "%";
}, 50);

Features

• Stylesheets CSS from <style> elements and style attributes cascades and inherits as in the browser, translated to ANSI color and decoration.
• Layout The CSS box model, flexbox, and table layout, computed in whole terminal cells with margins, borders, and padding.
• Scrolling Documents taller than the terminal scroll with window.scrollTo() and element.scrollIntoView().
• Events Keyboard, mouse, focus, and paste events fire on elements, the document, and the window, decoded from stdin.
• DOM utilities document.querySelector(), MutationObserver, ResizeObserver, and getBoundingClientRect() read the layout engine.
• Forms <input>, <textarea>, <select>, checkboxes, and radios have terminal-native looks, restylable with CSS; Tab and :focus work.
• Web Components customElements.define(), attachShadow(), <slot>, :host, and scoped styles; the built-in controls are shadow trees.
• Text CJK, emoji, and combining characters take correct widths; Hebrew and Arabic render in visual order with contextual shaping.
• Selection Drag to select, styled with ::selection; the caret moves by grapheme.
• Fullscreen Element.requestFullscreen() renders to the alternate screen; exiting restores the shell and its scrollback.

How it works

TermDOM implements the browser's rendering pipeline against a grid of character cells instead of pixels. CSS lengths map onto the grid — 1px is one row, 1ch is one column — so the box model, flexbox, and tables lay out in whole cells. On each frame the engine recomputes style and layout for whatever mutated, paints the result into a cell buffer, diffs it against the previous frame, and writes the difference to stdout as ANSI escape sequences. Input runs the other way: escape sequences from stdin are decoded into keyboard, mouse, and paste events and dispatched to DOM nodes.

Examples

• markdown.ts — a Markdown viewer that pages when the document is taller than the terminal.
• chat.ts — a streaming LLM chat client powered by ch.at, with a transcript and composer.
• todomvc.ts — the official TodoMVC with its component logic unmodified; only the stylesheet was swapped.
• fuzzy-finder.ts — a file picker that prints the selection to stdout.
• weather.ts — an emoji forecast from Open-Meteo, with a city search and flexbox day cards.
• popover.ts — a menu bar where every menu is a declarative popover; open, dismiss and stacking are the platform's.
• solitaire.ts — the Klondike solitaire above, with seeded deals playable by keyboard or mouse.

More runnable examples can be found in examples/.

Runtimes

TermDOM runs on Node, Bun and Deno. The library has no native components and can be used to create binaries with tools like bun build --compile.

Compatibility

COMPATIBILITY.md is generated by probing each feature against the engine.

Name

Not to be confused with DomTerm by Per Bothner, a terminal emulator built out of DOM elements. The two projects are each other's inverse: DomTerm puts a terminal in the DOM; TermDOM puts the DOM in a terminal.

License

MIT