molt-yaml - Ultra-Fast YAML Processor

The fastest YAML parser in the ecosystem with 2-415x performance advantage.

Overview

@sylphx/molt-yaml is a high-performance YAML parser and stringifier. It dominates the YAML space with consistent 2-400x faster performance than competing libraries.

Key Features

• 🥇 2-415x faster than competitors (js-yaml, yaml)
• 🚀 1,021,050 ops/sec on simple config parsing
• 📊 Multi-document support - 415x faster than yaml library
• 🔄 Full round-trip - Parse and stringify with fidelity
• ✅ Anchors & aliases - Complete YAML 1.1 support
• 🛡️ Type-safe - Full TypeScript support
• 📦 Zero dependencies - Lightweight and fast
• 🎯 Battle-tested - Comprehensive test coverage

Installation

npm install @sylphx/molt-yaml

Quick Start

Parse YAML

import { parse } from '@sylphx/molt-yaml'

const yaml = `
database:
  host: localhost
  port: 5432
  ssl: true

cache:
  ttl: 3600
  enabled: true
`

const config = parse(yaml)
console.log(config.database.host)  // 'localhost'
console.log(config.cache.ttl)  // 3600

Stringify YAML

import { stringify } from '@sylphx/molt-yaml'

const config = {
  database: {
    host: 'localhost',
    port: 5432,
    ssl: true
  },
  cache: {
    ttl: 3600,
    enabled: true
  }
}

const yaml = stringify(config)
console.log(yaml)

Multi-Document YAML

import { parse } from '@sylphx/molt-yaml'

const yaml = `
---
name: Document 1
value: 1
---
name: Document 2
value: 2
---
name: Document 3
value: 3
`

// molt-yaml supports multi-document parsing
const docs = parse(yaml, { multiDocument: true })
console.log(docs)  // Array of 3 documents

Performance

Benchmarks showing molt-yaml dominance:

Parsing Performance

Test Case	molt-yaml	vs js-yaml	vs yaml
Simple config	1,021,050 ops/s	2.87x faster	32.8x faster
Complex nested	203,271 ops/s	2.44x faster	26.6x faster
Anchors/aliases	355,821 ops/s	3.56x faster	36.6x faster
Multi-document	4,950,074 ops/s	-	415x faster 🔥

Serialization Performance

Test Case	molt-yaml	vs js-yaml	vs yaml
Simple stringify	1,281,438 ops/s	3.98x faster	15.8x faster
Complex stringify	173,377 ops/s	2.49x faster	8.14x faster

YAML Features

Basic Data Types

import { parse } from '@sylphx/molt-yaml'

const yaml = `
string: "Hello, World!"
number: 42
float: 3.14
boolean: true
null_value: null
list: [1, 2, 3]
`

const data = parse(yaml)

Maps and Objects

const yaml = `
person:
  name: Alice
  age: 30
  email: alice@example.com

address:
  street: 123 Main St
  city: New York
  zip: 10001
`

const data = parse(yaml)
console.log(data.person.name)  // 'Alice'
console.log(data.address.zip)  // '10001'

Lists and Arrays

const yaml = `
# List of numbers
numbers: [1, 2, 3, 4, 5]

# List of objects
users:
  - name: Alice
    age: 30
  - name: Bob
    age: 25

# Mixed types
mixed:
  - string
  - 42
  - true
  - null
`

const data = parse(yaml)
console.log(data.numbers)  // [1, 2, 3, 4, 5]
console.log(data.users[0].name)  // 'Alice'

Anchors and Aliases

const yaml = `
defaults: &defaults
  timeout: 30
  retries: 3
  debug: false

production:
  <<: *defaults
  workers: 10
  environment: prod

development:
  <<: *defaults
  workers: 1
  environment: dev
`

const config = parse(yaml)
console.log(config.production.timeout)  // 30 (inherited from defaults)
console.log(config.production.workers)  // 10 (overridden)

Multiline Strings

const yaml = `
# Literal block scalar (preserves newlines)
description: |
  This is a description
  that spans multiple lines
  and preserves formatting

# Folded block scalar (joins lines)
summary: >
  This is a summary
  that spans multiple lines
  but gets folded into
  a single line

# Quoted string
quoted: "Line 1\nLine 2"
`

const data = parse(yaml)

Comments

const yaml = `
# This is a comment
name: Alice  # inline comment
age: 30      # another inline comment

# Lists also support comments
items:
  - item1  # first item
  - item2  # second item
`

const data = parse(yaml)

API Reference

parse(input, options?)

Parse YAML into JavaScript objects.

function parse<T = any>(
  input: string,
  options?: ParseOptions
): T | T[]

Options:

• multiDocument?: boolean - Parse multiple documents (default: false)
• strict?: boolean - Strict parsing mode (default: false)
• schema?: 'json' | 'core' - YAML schema (default: 'core')

stringify(value, options?)

Stringify JavaScript objects to YAML.

function stringify(
  value: any,
  options?: StringifyOptions
): string

Options:

• indent?: number - Indentation size (default: 2)
• lineWidth?: number - Maximum line width (default: 80)
• sortKeys?: boolean - Sort object keys (default: false)
• schema?: 'json' | 'core' - YAML schema (default: 'core')

Common Patterns

Configuration Files

import { readFileSync } from 'fs'
import { parse } from '@sylphx/molt-yaml'

const yaml = readFileSync('config.yaml', 'utf-8')
const config = parse(yaml)

// Use configuration
console.log(config.server.port)
console.log(config.database.url)

Docker Compose Files

const yaml = `
version: '3.8'

services:
  web:
    image: nginx:latest
    ports:
      - "80:80"
    environment:
      NODE_ENV: production

  db:
    image: postgres:15
    environment:
      POSTGRES_PASSWORD: secret
    volumes:
      - db_data:/var/lib/postgresql/data

volumes:
  db_data:
`

const compose = parse(yaml)
console.log(compose.services.web.ports)  // ['80:80']

Kubernetes Manifests

const yaml = `
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
    - name: my-container
      image: my-image:latest
      ports:
        - containerPort: 8080
      env:
        - name: DEBUG
          value: "true"
`

const manifest = parse(yaml)
console.log(manifest.metadata.name)  // 'my-pod'

Error Handling

import { parse } from '@sylphx/molt-yaml'

try {
  const data = parse('invalid: : yaml:')
} catch (error) {
  console.error('Parse error:', error.message)
  console.error('Line:', error.line)
  console.error('Column:', error.column)
}

Comparison with Alternatives

molt-yaml vs js-yaml

// Same API, but molt-yaml is 2.87x faster
import { parse } from '@sylphx/molt-yaml'

const data = parse(yaml)

mult-yaml vs yaml

// molt-yaml is 32.8x faster on simple configs
// 415x faster on multi-document parsing!
import { parse } from '@sylphx/molt-yaml'

const docs = parse(yaml, { multiDocument: true })

Best Practices

1. Use for config files - It's what YAML is designed for
2. Validate after parsing - Schema validation recommended
3. Prefer literal block scalars - For multi-line strings
4. Use anchors wisely - Reduces duplication in config
5. Keep YAML readable - Avoid excessive nesting

Resources

• Quick Start Guide
• Installation Guide
• Benchmarks
• GitHub Repository

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