d3-zoomable-axis

A d3 axis you can drag to zoom. It combines a d3 axis (ticks, labels, domain line) with a dual-handle range control: drag the handles to select a [lo, hi] sub-range, which it emits in data space. One scale, one element — the axis is the zoom control, so it lines up with your chart by construction (no pixel-offset hacks).

▶ Live interactive demo — drag the axis handles to zoom a penguins scatterplot in your browser.

npm: @john-guerra/d3-zoomable-axis · status: early (0.0.x)

Two entry points

The package ships two independent layers — import only what you need:

Import	What you get
@john-guerra/d3-zoomable-axis	Core d3 component — zoomableAxis{Bottom,Top,Left,Right}, a d3-idiom factory applied via selection.call(...), built on d3-brush. Chainable accessors, d3-dispatch events. Dependency-light.
@john-guerra/d3-zoomable-axis/input	Accessible reactive widget — zoomableAxisInput, a DOM element with .value [lo, hi] that dispatches input (reactivewidgets.org / Observable view()). Native <input type=range> handles, a scented distribution overlay, drag-to-pan, editable value badges, and a live settings panel.

Splitting the entries keeps the core free of the widget's optional peer (reactive-widget-helper) and density deps (fast-kde, d3-shape) — those are only pulled in when you import /input.

Accessibility is a property of the widget layer: its handles are real <input type="range"> elements — keyboard-operable (arrows / Page / Home / End), screen-reader announced (named sliders with aria-valuetext), and standard HTML form inputs. The core zoomableAxis* factories are d3-brush-based (pointer/touch; not keyboard-accessible).

Install

npm install @john-guerra/d3-zoomable-axis
# for the widget layer, also install its optional peer:
npm install reactive-widget-helper

When bundling, the d3-* submodules (and, for the widget, fast-kde) come along as regular dependencies — nothing extra to do.

From a CDN (script tag) — core only

The UMD bundle is the core layer and is peer-global: to keep it small it does not embed d3, so load d3 first. The factories merge into the shared global d3:

<script src="https://cdn.jsdelivr.net/npm/d3@7"></script>
<script src="https://cdn.jsdelivr.net/npm/@john-guerra/d3-zoomable-axis"></script>
<script>
  // factories are merged into the shared global `d3`
  const slider = d3.zoomableAxisBottom(d3.scaleLinear().domain([24, 92]).range([0, 600]));
</script>

The widget layer is ESM-only; import it from a bundler, or over ESM from https://cdn.jsdelivr.net/npm/@john-guerra/d3-zoomable-axis/src/input.js.

Core component (d3 idiom)

import * as d3 from "d3";
import { zoomableAxisBottom } from "@john-guerra/d3-zoomable-axis";

const x = d3.scaleLinear().domain([24, 92]).range([0, 600]);

const slider = zoomableAxisBottom(x)
  .step(1)
  .ticks(10)
  .value([30, 60])                  // initial [lo, hi] in data space
  .on("input", (v) => chart.zoomX(v))  // fires while dragging
  .on("end",   (v) => persist(v));

d3.select("svg").append("g")
  .attr("transform", "translate(20,40)")
  .call(slider);

slider.value();          // -> [30, 60]
slider.value([40, 70]);  // set + re-render, no event

Factories: zoomableAxisBottom, zoomableAxisTop, zoomableAxisLeft, zoomableAxisRight (orientation mirrors d3-axis). Accessors: scale, value, step, handleSize, ticks, tickArguments, tickValues, tickFormat, tickSize, tickSizeInner, tickSizeOuter, tickPadding, on. Events (d3-dispatch): start, input, end — each receives [lo, hi] in data space (inverted from pixels, snapped to step). Imperative slider.move(g, [lo,hi]) sets and emits; slider.value([lo,hi]) sets silently.

Handles: the core is d3-brush-based, so its resize handles are invisible hit-areas by default — only the selection is drawn. Style .selection / .handle (or set .handleSize(...)) to draw them. The widget layer below ships visible, accessible handles out of the box.

Reactive widget (Observable / reactivewidgets.org)

import { zoomableAxisInput } from "@john-guerra/d3-zoomable-axis/input";

const weeks = view(zoomableAxisInput([24, 92], {
  orient: "bottom", step: 1, length: 600, value: [30, 60],
  label: "Weeks", units: "wk",
}));
// `weeks` is reactive [lo, hi]; the element has .value and dispatches "input".

Drag a handle to resize an end, drag the band between the handles to pan the window, or double-click a value badge to type an exact value (an OS-native number / date / datetime-local / time picker, via the inputType option). Every handle is a keyboard-focusable native slider.

Key options: orient, step, length, value, label, units, format, inputType ("number" | "date" | "time" | "datetime-local"), ticks, thickness, margin, and scent (below). Events: input (DOM, on the element) plus start / input / end / scent via el.on(...).

Scented distribution

Pass scent to draw the data distribution along the axis (a scented widget — see where the data is dense before you zoom). A ⚙ settings panel lets you retune it live.

zoomableAxisInput([170, 235], {
  orient: "bottom", length: 600, value: [190, 215],
  scent: {
    values: flipperLengths,   // number[]
    type: "histogram",        // "histogram" | "violin" | "area"
    bins: 28,
    direction: "out",         // "out" = away from the plot, "in" = toward it
  },
});

scent options: type, bins, size, direction ("out" | "in"; histogram + area only — side is an alias), style ("kde" | "bars"), color, colorSelected, KDE tunables (bandwidth, adjust, pad), curve (a d3-shape curve factory or name string), controls (the ⚙ panel — on by default; false to hide), and persistKey (remember tuned params in localStorage). Panel edits also fire a scent event (el.on("scent", params => …)).

See it live: john-guerra.github.io/d3ZoomableAxis (a landing page + demo that import the published npm package from a CDN). The source is in examples/demo.html — live zoom, dynamic-query filtering, and a brush-synced example (and examples/test-local.html for an offline smoke test).

Design & background

• docs/DESIGN.md — architecture, API, packaging.
• docs/d3-api-style.md — the d3 reusable-component idiom reference.
• docs/history-direct-manipulation-rangesliders.md — Shneiderman & Plaisant dynamic-query range sliders and design takeaways.

License

MIT © John Alexis Guerra Gómez