swisseph-wasm

SwissEph Examples

This directory contains practical examples demonstrating how to use the SwissEph WebAssembly library for various astronomical and astrological calculations.

Examples Overview

1. `basic-usage.js`

Fundamental operations and core functionality:

Basic planetary position calculations
Multiple planet calculations
Time zone handling
Sidereal vs tropical comparisons
Date conversion functions
Degree utilities
Library information

Run with:

node examples/basic-usage.js

2. `birth-chart.js`

Complete birth chart calculation system:

Full birth chart calculator class
Planetary positions with zodiac signs
House calculations
Additional astrological points (nodes, Lilith, Chiron)
Aspect calculations
Professional-grade chart interpretation

Run with:

node examples/birth-chart.js

3. `advanced-features.js` (Coming Soon)

Advanced astronomical calculations:

Eclipse predictions
Rise/set/transit times
Fixed star positions
Topocentric calculations
Atmospheric refraction
Coordinate transformations

4. `web-integration.js` (Coming Soon)

Browser integration examples:

HTML/JavaScript integration
Real-time calculations
Interactive charts
Performance optimization
Error handling in web environments

Quick Start

Basic Planetary Position

import SwissEph from '../src/swisseph.js';

const swe = new SwissEph();
await swe.initSwissEph();

const jd = swe.julday(2023, 6, 15, 12.0);
const sunPos = swe.calc_ut(jd, swe.SE_SUN, swe.SEFLG_SWIEPH);

console.log(`Sun longitude: ${sunPos[0]}°`);
swe.close();

Birth Chart Calculation

import { BirthChartCalculator } from './examples/birth-chart.js';

const calculator = new BirthChartCalculator();

const chart = await calculator.calculateBirthChart({
  year: 1990, month: 5, day: 15,
  hour: 14, minute: 30, timezone: -5,
  latitude: 40.7128, longitude: -74.0060
});

console.log(chart.planets);
calculator.destroy();

Example Output

Basic Planetary Positions

=== Basic Planetary Position ===
Julian Day: 2460110.0
Sun Position:
  Longitude: 84.123456°
  Latitude: 0.000123°
  Distance: 1.015678 AU
  Speed: 0.958765°/day
  Zodiac: 24.12° Gemini

Birth Chart

PLANETARY POSITIONS:
===================
☉ Sun       : 24.12° Taurus (54.12°)
☽ Moon      : 15.67° Scorpio (225.67°)
☿ Mercury   : 8.45° Gemini (68.45°)
♀ Venus     : 2.89° Cancer (92.89°)
♂ Mars      : 18.34° Virgo (168.34°)
♃ Jupiter   : 12.78° Pisces (342.78°)
♄ Saturn    : 25.91° Capricorn (295.91°)
♅ Uranus    : 7.23° Capricorn (277.23°)
♆ Neptune   : 11.45° Capricorn (281.45°)
♇ Pluto     : 16.78° Scorpio (226.78°)

MAJOR ASPECTS:
==============
Sun ☌ Mercury: Conjunction (orb: 2.34°)
Moon ☍ Venus: Opposition (orb: 3.21°)
Mars △ Jupiter: Trine (orb: 1.87°)

Common Patterns

Error Handling

async function safeCalculation() {
  let swe = null;
  try {
    swe = new SwissEph();
    await swe.initSwissEph();
    // calculations here
    return result;
  } catch (error) {
    console.error('Calculation failed:', error);
    return null;
  } finally {
    if (swe) swe.close();
  }
}

Batch Processing

async function calculateMultipleDates(dates) {
  const swe = new SwissEph();
  await swe.initSwissEph();
  
  const results = [];
  for (const date of dates) {
    const jd = swe.julday(date.year, date.month, date.day, date.hour);
    const pos = swe.calc_ut(jd, swe.SE_SUN, swe.SEFLG_SWIEPH);
    results.push({ date, position: pos[0] });
  }
  
  swe.close();
  return results;
}

Reusable Calculator Class

class AstrologyCalculator {
  constructor() {
    this.swe = null;
    this.initialized = false;
  }
  
  async init() {
    if (!this.initialized) {
      this.swe = new SwissEph();
      await this.swe.initSwissEph();
      this.initialized = true;
    }
  }
  
  async calculate(params) {
    await this.init();
    // calculations here
  }
  
  destroy() {
    if (this.swe) {
      this.swe.close();
      this.swe = null;
      this.initialized = false;
    }
  }
}

Running Examples

Prerequisites

Node.js 14+ or modern browser
ES6 modules support

Command Line

# Run basic usage examples
node examples/basic-usage.js

# Run birth chart example
node examples/birth-chart.js

# Run specific function
node -e "import('./examples/basic-usage.js').then(m => m.basicPlanetaryPosition())"

Browser

<script type="module">
  import { runAllExamples } from './examples/basic-usage.js';
  runAllExamples();
</script>

Tips for Development

Always initialize: Call await swe.initSwissEph() before calculations
Clean up: Always call swe.close() when done
Handle time zones: Convert to UTC before calculations
Validate inputs: Check date ranges and parameter validity
Use constants: Use library constants instead of magic numbers
Batch operations: Reuse SwissEph instance for multiple calculations
Error handling: Wrap calculations in try-catch blocks

Performance Considerations

Initialize once, calculate many times
Use appropriate calculation flags
Clean up resources properly
Consider WebWorkers for heavy calculations
Cache results when appropriate