xalen-ephemeris (WASM)

Pure-Rust astronomical ephemeris for astrology, compiled to WebAssembly — Vedic charts, panchang, houses, dasha, and compatibility in any browser or Node.js. Zero data files, zero native dependencies.

Part of the XALEN Ephemeris suite — pure-Rust core, zero unsafe in the math, thread-safe, Apache-2.0. This package is the WebAssembly build (runs in the browser and in Node). For a faster, synchronous native Node addon, use the xalen package instead.

This crate wraps the XALEN core crates behind a single XalenWasm handle exported to JavaScript via wasm-bindgen. The same handle also compiles to native Rust, so it can be exercised in ordinary cargo test.

Install

# FORTHCOMING — not on npm yet.
npm install xalen-ephemeris

Pre-publish note: xalen-ephemeris is not on npm yet (the badge above is a placeholder). Until it ships, build the package from the repo:

git clone https://github.com/vedika-io/xalen-ephemeris.git
cd xalen-ephemeris/crates/xalen-wasm
wasm-pack build --target web        # browser; or --target nodejs / --target bundler
# emits pkg/ with xalen_wasm_bg.wasm, xalen_wasm.js, and xalen_wasm.d.ts

Platform support

WebAssembly is platform-independent: a single .wasm artifact runs on every CPU and OS — any modern browser and any Node.js ≥ 16. There is no per-platform build to select.

scripts/build-all-platforms.sh wasm produces the package locally; the durable build runs on every v* tag in .github/workflows/release.yml (wasm-pack build --target web → wasm-pack publish). The crate compiles wasm32-unknown-unknown only; the same XalenWasm handle also builds natively for cargo test.

Usage

In the browser (--target web):

import init, { XalenWasm } from "./pkg/xalen_wasm.js";
await init();

const w = new XalenWasm();
const J2000 = 2451545.0;

// Full Vedic chart for Pune (18.52 N, 73.85 E), Lahiri ayanamsa (id 0).
const chart = JSON.parse(w.fullChartJson(J2000, 18.52, 73.85, 0));
console.log(chart.planets.Sun, chart.ascendant_deg);

In Node (--target nodejs):

const { XalenWasm } = require("xalen-ephemeris");
const w = new XalenWasm();
const aya = XalenWasm.ayanamsaDeg(2451545.0, 0); // Lahiri at J2000 ≈ 23.85°

API

The XalenWasm handle is constructed once (new XalenWasm()) and serves the instance methods; the time/ayanamsa helpers are static.

Planetary positions

• tropicalLongitude(jdUt1, bodyId) / siderealLongitude(jdUt1, bodyId, ayanamsaId) — a single longitude in degrees. Ketu (body 13) is derived as Rahu + 180°.
• planetPositionJson(jdUt1, bodyId, sidereal, ayanamsaId) — the full state pyswisseph returns from swe.calc_ut(..., FLG_SPEED) plus a retrograde flag: { longitude, latitude, distance, lon_speed, lat_speed, dist_speed, is_retrograde }. Angles/speeds in degrees (speeds per day); distance in AU. When sidereal is true, the longitude is made sidereal and the ayanamsa's own precession rate is removed from lon_speed (matching Swiss SEFLG_SIDEREAL | SEFLG_SPEED); is_retrograde is taken from the frame-independent tropical rate.

Body IDs: 0=Sun 1=Moon 2=Mercury 3=Venus 4=Mars 5=Jupiter 6=Saturn 7=Uranus 8=Neptune 9=MeanNode(Rahu) 10=TrueNode 11=Pluto 12=Chiron 13=Ketu.

Charts & Vedic

• fullChartJson(jdUt1, lat, lon, ayanamsaId) — the nine grahas (each { longitude, nakshatra, pada, rashi }) plus Whole-Sign ascendant_deg, mc_deg, and ayanamsa_deg.
• panchangJson(jdUt1, ayanamsaId) — the five limbs (tithi, vara, nakshatra, yoga, karana).
• housesJson(jdUt1, lat, lon, systemId) — house cusps across 14 systems (0=WholeSign 1=Equal 2=Placidus 3=Koch … 13=Krusinski).
• getNakshatra(moonSiderealDeg) — nakshatra name (string).
• nakshatraInfoJson(siderealDeg) — structured { name, pada, lord, deity, index }, the one-contract shape shared with the Python/Node bindings.
• getRashi(siderealDeg) — rashi name (string).
• vimshottariDasha(moonDeg, birthJd) — all 9 Mahadashas, each with Antardasha sub-periods (JSON array).
• divisionalChart(lonDeg, varga) — the divisional (Varga) sign for D1, D2, D3, D4, D7, D9, D10, D12, D16, D20, D24, D27, D30, D40, D45, D60.

Compatibility

• compatibility(boyMoonDeg, girlMoonDeg) — Ashta Koota (8-fold) match from sidereal Moon longitudes in degrees (0–360); returns the 8 koota scores and total (out of 36). Both nakshatra and rashi are resolved from the longitude, so a Moon near a sign boundary maps to the correct rashi.

Time & ayanamsa helpers (static)

• XalenWasm.julianDay(year, month, day, hour) — calendar (proleptic Gregorian, UT) to Julian Day.
• XalenWasm.ayanamsaDeg(jdUt1, ayanamsaId) — ayanamsa value (17 systems).
• XalenWasm.deltaT(jd) — ΔT (TT − UT1) in seconds (SMH 2016 model).
• XalenWasm.bodyName(bodyId) — body name string.

Functions that take a longitude or JD return an error string (thrown value on the JS side) for non-finite or out-of-range input rather than silently returning NaN.

// The handle also runs natively, so it is testable without a browser:
use xalen_wasm::XalenWasm;
let w = XalenWasm::new();
let jd = XalenWasm::julian_day(2000, 1, 1, 12.0);
let aya = XalenWasm::ayanamsa_deg(jd, 0).unwrap();   // Lahiri ≈ 23.85°
assert!(aya > 23.0 && aya < 25.0);
let chart = w.full_chart_json(jd, 18.52, 73.85, 0).unwrap();
assert!(chart.contains("Sun") && chart.contains("Moon"));

Accuracy — honest bounds

Positions and derived quantities come from the XALEN core crates (VSOP87A + IAU 2000B nutation; ELP2000-82 for the Moon), cross-validated against JPL Horizons (DE440), the official VSOP87 check file, and Swiss Ephemeris. XALEN matches these references — DE440 is the reference, we do not "beat" it. Measured bounds (20k-chart bound vs DE440): Sun 0.21″, Mercury–Saturn ≤ 0.76″ (sub-arcsecond); Uranus 1.78″, Neptune 2.53″; Moon ~3″ RMS analytical; Pluto ~1 arcminute in-window. vs Swiss: 0 of 5,000,000 charts over 0.1° for any planet/node, 1850–2150. The genuine differentiator is pure Rust, zero unsafe core, thread-safe, Apache-2.0, WebAssembly-ready. Full report → docs/ACCURACY.md and CREDITS.md.

TypeScript

wasm-pack emits xalen_wasm.d.ts alongside the .wasm, typing the XalenWasm class and every method, so TypeScript consumers get full autocomplete.

License

Apache-2.0. See LICENSE.