Candlestick

A modern, modular JavaScript library for candlestick pattern detection. Detects classic reversal and continuation patterns in OHLC data, with a clean API and no native dependencies.

✨ Highlights:

• 🎯 18 candlestick patterns, 29 variants across single, two, and three-candle formations
• 📦 ESM & CommonJS support (dual export)
• 🔷 Full TypeScript definitions with IntelliSense
• ✅ 347 tests — 99.75% line coverage, 100% function coverage
• 🚀 Streaming API for massive datasets (~70% memory reduction)
• 🔬 Property-based testing with fast-check (1000+ generated scenarios)
• 🔌 Plugin system for custom patterns
• ✅ Data validation (validateOHLC, validateOHLCArray)
• 📊 Pattern metadata (confidence, strength, type, direction)
• 💻 CLI tool for CSV/JSON analysis

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Table of Contents

• Why Candlestick?
• Features
• Quick Start
• Usage
• Pattern Detection Functions
• High-Level Pattern Chaining
• Pattern Descriptions
• Examples
• Full Example Files
• Linting & Formatting
• Running Tests
• Contributing
• Changelog
• FAQ
• Roadmap
• Code of Conduct
• License

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Why Candlestick?

• No native dependencies: 100% JavaScript, works everywhere Node.js runs.
• Modular: Each pattern is its own module, easy to extend or customize.
• Consistent API: All pattern functions use a standard interface.
• Pattern Chaining: Scan for multiple patterns in a single pass.
• Comprehensive Test Suite: Each pattern and utility is unit tested.
• Modern Tooling: Uses ESLint (flat config) and Prettier for code quality and formatting.
• Actively Maintained: See ROADMAP.md and CHANGELOG.md.

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Features

• 18 Candlestick Patterns (29 variants): Comprehensive pattern detection library
• Streaming API: Process massive datasets with 70% memory reduction
• Property-Based Testing: Validated with 1000+ generated test cases
• Dual Module Support: CommonJS and ESM exports
• TypeScript: Complete type definitions with IntelliSense
• Data Validation: Robust OHLC validation system
• Plugin System: Register custom patterns
• Pattern Chaining: Multi-pattern detection in single pass
• Zero Dependencies: Pure JavaScript, works everywhere
• Excellent Test Coverage: 347 tests with 99.75% coverage (97.63% branches, 100% functions)
• High Performance: 59K+ candles/sec throughput
• Well Documented: Architecture guides, examples, and API docs

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Quick Start

Installation

npm install candlestick

CommonJS (Node.js)

const { isHammer, hammer, patternChain, allPatterns } = require("candlestick");

// Check single candle (small body in upper third, long lower shadow, tiny upper shadow)
const candle = { open: 14, high: 15, low: 8, close: 14.5 };
console.log(isHammer(candle)); // true

// Find patterns in series
const candles = [
  /* array of OHLC objects */
];
console.log(hammer(candles)); // [indices where pattern found]

// Detect all patterns at once
const results = patternChain(candles, allPatterns);
console.log(results); // [{ index, pattern, match }]

ESM (Modern JavaScript)

import { isHammer, hammer, patternChain, allPatterns } from "candlestick";

const candles = [
  /* array of OHLC objects */
];
const results = patternChain(candles, allPatterns);
console.log(results);

TypeScript

import { OHLC, PatternMatch, patternChain, allPatterns } from "candlestick";

const candles: OHLC[] = [
  { open: 10, high: 15, low: 8, close: 12 },
  { open: 12, high: 16, low: 11, close: 14 },
];

const results: PatternMatch[] = patternChain(candles, allPatterns);
// Full IntelliSense support ✓

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Usage

Importing

CommonJS (Node.js):

// Import all patterns
const candlestick = require("candlestick");

// Or import only what you need
const { isHammer, hammer, patternChain } = require("candlestick");

ESM (Modern JavaScript):

// Import all patterns
import candlestick from "candlestick";

// Or import only what you need (recommended for tree-shaking)
import { isHammer, hammer, patternChain } from "candlestick";

OHLC Format

All functions expect objects with at least:

{
  open: Number,
  high: Number,
  low: Number,
  close: Number
}

Extra fields (date, volume, etc.) are preserved unchanged and passed through to every match result, so you can attach any metadata you need:

const data = [
  {
    date: "2024-01-06",
    open: 41490,
    high: 41500,
    low: 39200,
    close: 41500,
    volume: 61000,
  },
  // ...
];

const results = patternChain(data, allPatterns);
console.log(results[0].match[0].date); // "2024-01-06"
console.log(results[0].match[0].volume); // 61000

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Pattern Detection Functions

Boolean (Single/Pair) Detection

Single candle:

• isHammer(candle) / isBullishHammer(candle) / isBearishHammer(candle)
• isInvertedHammer(candle) / isBullishInvertedHammer(candle) / isBearishInvertedHammer(candle)
• isDoji(candle)
• isMarubozu(candle) / isBullishMarubozu(candle) / isBearishMarubozu(candle)
• isSpinningTop(candle) / isBullishSpinningTop(candle) / isBearishSpinningTop(candle)

Two candles:

• isBullishEngulfing(prev, curr) / isBearishEngulfing(prev, curr)
• isBullishHarami(prev, curr) / isBearishHarami(prev, curr)
• isBullishKicker(prev, curr) / isBearishKicker(prev, curr)
• isHangingMan(prev, curr) / isShootingStar(prev, curr)
• isPiercingLine(prev, curr) / isDarkCloudCover(prev, curr)
• isTweezers(prev, curr) / isTweezersTop(prev, curr) / isTweezersBottom(prev, curr)

Three candles:

• isMorningStar(c1, c2, c3) / isEveningStar(c1, c2, c3)
• isThreeWhiteSoldiers(c1, c2, c3) / isThreeBlackCrows(c1, c2, c3)

Array (Series) Detection

Single candle:

• hammer(dataArray) / bullishHammer(dataArray) / bearishHammer(dataArray)
• invertedHammer(dataArray) / bullishInvertedHammer(dataArray) / bearishInvertedHammer(dataArray)
• doji(dataArray)
• marubozu(dataArray) / bullishMarubozu(dataArray) / bearishMarubozu(dataArray)
• spinningTop(dataArray) / bullishSpinningTop(dataArray) / bearishSpinningTop(dataArray)

Two candles:

• bullishEngulfing(dataArray) / bearishEngulfing(dataArray)
• bullishHarami(dataArray) / bearishHarami(dataArray)
• bullishKicker(dataArray) / bearishKicker(dataArray)
• hangingMan(dataArray) / shootingStar(dataArray)
• piercingLine(dataArray) / darkCloudCover(dataArray)
• tweezers(dataArray) / tweezersTop(dataArray) / tweezersBottom(dataArray)

Three candles:

• morningStar(dataArray) / eveningStar(dataArray)
• threeWhiteSoldiers(dataArray) / threeBlackCrows(dataArray)

All array functions return an array of indices where the pattern occurs.

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High-Level Pattern Chaining

Scan a series for multiple patterns in one pass:

const { patternChain, allPatterns } = require("candlestick");

const matches = patternChain(dataArray, allPatterns);
// matches: [
//   { index: 3, pattern: 'hammer', match: [candleObj] },
//   { index: 7, pattern: 'bullishEngulfing', match: [candleObj, candleObj] },
//   ...
// ]

You can also pass a custom list of patterns:

const { patternChain, doji, bullishEngulfing } = require("candlestick");

const matches = patternChain(dataArray, [
  { name: "doji", fn: doji },
  { name: "bullishEngulfing", fn: bullishEngulfing, paramCount: 2 },
]);

Strict Mode

Pass { strict: true } to throw on invalid OHLC data instead of silently skipping:

patternChain(dataArray, allPatterns, { strict: true });
// throws if any candle has high < low, NaN fields, etc.

Multi-candle patterns: Two-candle patterns (Engulfing, Harami, Kicker, Hanging Man, Shooting Star, Piercing Line, Dark Cloud Cover, Tweezers Top/Bottom) return a match array with 2 candles. Three-candle patterns (Morning Star, Evening Star, Three White Soldiers, Three Black Crows) return 3. Single-candle patterns return 1. This is driven by the paramCount property on each pattern definition.

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Pattern Descriptions

Single Candle Patterns

• Hammer: Small body near the top (body < 1/3 of range), long lower shadow (tail ≥ 2× body), small upper shadow. Signals possible bullish reversal.
• Inverted Hammer: Small body near the bottom, long upper shadow (wick ≥ 2× body), small lower shadow. Bullish reversal signal.
• Doji: Very small body (body < 10% of range), open ≈ close. Indicates indecision. Candle must have range (high > low).
• Marubozu: Long body (≥ 70% of range) with minimal shadows (< 10% of body). Strong directional move. Bullish Marubozu shows strong buying, Bearish shows strong selling.
• Spinning Top: Small body (< 30% of range) with long upper and lower shadows (each > 20% of range). Indicates market indecision or potential reversal.

Two Candle Patterns

• Engulfing: Second candle's body fully engulfs the previous (body range covers previous body). Bullish or bearish.
• Harami: Second candle's body is inside the previous (body range within previous body). Bullish or bearish.
• Kicker: Opposite-color candles with a body gap between them (second body does not overlap first body). The second candle must not be a Hammer or Inverted Hammer shape. Bullish or bearish.
• Hanging Man: Bullish candle followed by a bearish hammer with a gap up. Bearish reversal.
• Shooting Star: Bullish candle followed by a bearish inverted hammer with a gap up. Bearish reversal.
• Piercing Line: Bullish reversal. Bearish candle (body ≥ 50% of range) followed by bullish candle (body ≥ 50% of range) that opens below first's low, closes above the first body's midpoint but below the first body's top (i.e., does not fully engulf).
• Dark Cloud Cover: Bearish reversal. Bullish candle (body ≥ 50% of range) followed by bearish candle (body ≥ 50% of range) that opens above first's high, closes below the first body's midpoint but above the first body's bottom (i.e., does not fully engulf).
• Tweezers Top: Bearish reversal. Bullish candle followed by bearish candle with matching highs (within 1% of the candles' average range). Both candles must have significant bodies (≥ 40% of their range). Indicates resistance level.
• Tweezers Bottom: Bullish reversal. Bearish candle followed by bullish candle with matching lows (within 1% of the candles' average range). Both candles must have significant bodies (≥ 40% of their range). Indicates support level.

Three Candle Patterns

• Morning Star: Bullish reversal. Long bearish candle (body ≥ 60% of range), small-bodied star (body ≤ 30% of range) whose body gaps down from the first candle's body, long bullish candle (body ≥ 60% of range) closing above the midpoint of the first candle's body.
• Evening Star: Bearish reversal. Long bullish candle (body ≥ 60% of range), small-bodied star (body ≤ 30% of range) whose body gaps up from the first candle's body, long bearish candle (body ≥ 60% of range) closing below the midpoint of the first candle's body.
• Three White Soldiers: Three consecutive bullish candles, each opening within the previous body and closing higher. Each body ≥ 60% of its candle's range; upper shadows ≤ 30% of body. Signals strong bullish continuation/reversal.
• Three Black Crows: Three consecutive bearish candles, each opening within the previous body and closing lower. Each body ≥ 60% of its candle's range; lower shadows ≤ 30% of body. Signals strong bearish continuation/reversal.

Note: The library does not mutate your input data. Pattern functions return arrays of indices; precomputeCandleProps returns new enriched candle objects. If you call individual pattern series functions (e.g., hammer(), doji()) multiple times on the same raw array, precompute once for better performance (see below). When using patternChain, precomputation is handled internally and no manual call is needed.

Performance: precomputeCandleProps

When calling multiple pattern functions on the same dataset, use `precomputeCandleProp