Changelog¶

This page mirrors the project changelog. The canonical source lives at docs/CHANGELOG.md in the repository.

All notable changes to this project are documented here.

1.2.3 — 2026-05-21¶

Multi-line area fills now layer correctly when one series is bigger in some regions and smaller in others. The previous version sorted whole series by their global peak, so a series that had one tall spike would sit on top of (or under) every other series across the entire chart. Areas are now split into per-segment trapezoids and sorted by their local height, so layering can flip from segment to segment and a small bar in one region no longer "phases through" a taller neighbour.
HTML page card charts no longer print a duplicated title in the SVG. Passing title: '' to any renderer now suppresses the default title fallback (the cards already show the symbol/name in their own header).
renderBarChart and renderCandlestickChart insets the first and last bar by half their width so they sit fully inside the plot rectangle instead of overflowing into the axis area.
parseInterval / parseIntervalSpec now reject zero-length intervals like "0d" or "0mo" (previously accepted, would have produced bars sharing the same timestamp).

Multi-line chart area: true option. Each series gets a translucent gradient fill from the line down to the chart bottom. Areas are painted from largest peak to smallest so smaller series stay visible on top of taller ones.
Sub-cent price support. Internal floor moved from 0.01 to 0.0001, and prices below $1 keep 4 decimal places (below $0.01 keeps 6). Custom prices/ohlc arrays accept any positive number down to 0.0001.
Axis labels auto-format with extra decimals when prices are small, so a chart of $0.0008 tokens shows readable values instead of rounding to zero.

Multi-line chart legend now sits in the top-left of the plot area instead of top-right
Chart titles move to the top-right so they don't overlap the legend
Default chart size is now 1000×500 (was 800×400)
Default xTicks is now 8 (was 5) so timelines have more date labels out of the box

renderMultiLineChart(stocks, options) — render multiple companies on a single chart with a built-in legend. Series are plotted against actual timestamps, so stocks with different startDate values land at the right horizontal position (a 2020 series sits on the left, a 2022 series on the right). Supports mode: 'price' (raw prices) or mode: 'normalized' (rebased to 100, the default).
kind: 'stock' | 'crypto' option on generateStock. Crypto uses log-distributed start prices (sub-$1 coins to $50k+), wider drift and much higher volatility. Defaults to 'stock'.
Stock objects now carry a kind field, preserved through toJSON / fromJSON.
Per-stock color field is honored by the multi-line renderer; otherwise a built-in palette assigns colors automatically.
xTicks and yTicks chart options to control the number of date / price labels (defaults to 5 each).
fromJSON now accepts arrays of stocks, so a market saved with toJSON(market) round-trips back into an array you can pass straight to renderMultiLineChart.

The chart title option (already in the API) is the image title — completely separate from a stock's symbol and name. Pass any string and it appears at the top of the SVG: renderLineChart(stock, { title: 'Q1 Review' }).

Edge axis labels no longer get cropped: the first X-axis label is left-anchored at the plot edge and the last is right-anchored, so long dates like 2023-12-31 stay fully inside the chart
Slightly bigger default padding (top: 28, right: 24, bottom: 44, left: 64) so longer price labels and date strings have breathing room

1mo and 1y intervals are now calendar-aware. Bars step to the same day of the next month/year instead of advancing by 30 or 365 fixed days, so startDate: '1999-08-01' with 1mo produces 1999-08-01, 1999-09-01, 1999-10-01, … and 1y produces 1999-08-01, 2000-08-01, 2001-08-01, …
Y-axis padding is clipped at zero so charts of low-priced series never show negative tick labels
X-axis labels switch to full YYYY-MM-DD when the chart spans more than one calendar year (instead of ambiguous MM/DD)

parseIntervalSpec and stepTime helpers in src/interval.js for calendar-aware time stepping

prices option on generateStock — pass your own close prices, the package fills in open/high/low/volume around them
ohlc option on generateStock — pass full OHLC bars verbatim
toJSON(stockOrMarket) — convenience wrapper around JSON.stringify
fromJSON(text|object) — parse and validate previously saved data, ready to render again
Validation for the new inputs: rejects negative prices, malformed bars, and the prices/ohlc conflict
README rewritten with a glossary, a step-by-step tutorial, and a recipes section

examples/market-page.js now uses the default line chart instead of area
renderHtmlPage now produces clickable cards: clicking one opens a detail view with a larger chart, key stats, and a recent-bars table; press Escape or click outside to close
Larger fonts and bigger card charts on the generated HTML page so labels are readable
SVG axis and title fonts bumped from 11/13 px to 13/15 px

Initial release. A modern rewrite of the old fake-stock-market-generator.

generateStock(options) — single ticker with OHLCV bars
generateMarket({ count, stocks, ...options }) — whole markets, with optional per-company overrides
Geometric Brownian Motion price model (prices stay positive, configurable drift and volatility)
User-driven metadata: symbol defaults to a random ticker, name and sector are yours to set
Configurable: symbol, name, sector, startPrice, drift, volatility, bars, interval, startDate, seed
Interval shorthands: "1m", "1h", "1d", "1w", "1mo", "1y", plus raw milliseconds
Seeded PRNG (Mulberry32 + Box-Muller) for reproducible output
renderLineChart, renderAreaChart, renderBarChart, renderCandlestickChart — SVG renderers
renderChart(stock, type, options) — single entry point
renderHtmlPage(marketOrStock, options) — self-contained HTML page builder
Light and dark themes, with per-color overrides
Dual ESM + CJS publish, zero runtime dependencies
Node 14+ support
Input validation: rejects negative startPrice, non-string name/sector/symbol, negative volatility, non-finite drift, invalid startDate, and non-positive bars