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- Trim README to ≤80 lines with wiki link for full docs - Add CHANGELOG.md with initial entry - Fix CI: replace pinned pnpm/action-setup with corepack enable - Add "type": "module" and flat exports map (ADR-015) - Add ./package.json exports entry - Add coverage script - Rename lib/spa.js → lib/spa.cjs to fix CJS/ESM conflict under "type": "module" - Update src/index.ts and tsup.config.ts to reference spa.cjs - Add .github/wiki pages: _Sidebar, _Footer, Contributing, SECURITY, CODE_OF_CONDUCT
67 lines
2.3 KiB
Markdown
67 lines
2.3 KiB
Markdown
# nrel-spa
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[](https://www.npmjs.com/package/nrel-spa)
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[](https://github.com/acamarata/nrel-spa/actions/workflows/ci.yml)
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[](./LICENSE)
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Pure JavaScript implementation of the NREL Solar Position Algorithm (SPA). Computes solar zenith angle, azimuth, sunrise, sunset, and solar noon for any location and date. Zero dependencies, synchronous. Validated to produce identical results to the original NREL C reference implementation.
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## Installation
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```bash
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npm install nrel-spa
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```
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## Quick Start
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```javascript
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import { getSpa, calcSpa } from 'nrel-spa';
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const date = new Date('2025-06-21T00:00:00Z');
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// Raw fractional hours
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const raw = getSpa(date, 40.7128, -74.006, -4); // New York, EDT
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console.log(raw.sunrise); // 5.417
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console.log(raw.solarNoon); // 12.965
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console.log(raw.sunset); // 20.509
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// Formatted HH:MM:SS strings
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const fmt = calcSpa(date, 40.7128, -74.006, -4);
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console.log(fmt.sunrise); // "05:25:03"
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console.log(fmt.solarNoon); // "12:57:56"
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console.log(fmt.sunset); // "20:30:35"
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```
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CommonJS:
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```js
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const { getSpa } = require('nrel-spa');
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```
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Pass a `zenith angles` array as the sixth argument to `getSpa`/`calcSpa` for civil (96°), nautical (102°), or astronomical (108°) twilight times.
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## TypeScript
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```typescript
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import { getSpa, calcSpa, formatTime, SPA_ZA_RTS } from 'nrel-spa';
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import type { SpaOptions, SpaResult, SpaFunctionCode } from 'nrel-spa';
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```
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## Documentation
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Full API reference, algorithm notes, and twilight calculation guide: [GitHub Wiki](https://github.com/acamarata/nrel-spa/wiki)
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## Related
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- [solar-spa](https://www.npmjs.com/package/solar-spa): WASM build of the same algorithm, async, for high-throughput batch work
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- [pray-calc](https://www.npmjs.com/package/pray-calc): Islamic prayer times built on nrel-spa
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## Acknowledgments
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The core algorithm is a JavaScript port of the NREL SPA by Ibrahim Reda and Afshin Andreas:
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> Reda, I., Andreas, A. (2004). "Solar Position Algorithm for Solar Radiation Applications." Solar Energy, 76(5), 577-589.
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## License
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MIT (TypeScript wrapper and build tooling). The core algorithm in `lib/spa.js` is a port of NREL's SPA C source, subject to its own terms. See [LICENSE](./LICENSE).
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