@bemoje/decorators

TypeScript decorators for lazy property initialization and method memoization.

Exports

• lazyProp: Decorator to memoize a method or getter accessor property.
• memoizeAsync: Decorator to memoize an async method. Uses memoizee library, so if params are objects, the decorator needs a normalizer function.
• memoizeSync: Decorator to memoize a sync method.

Installation

npm install @bemoje/decorators

Usage

Lazy Properties

Defer expensive computation until first access, then cache the result:

import { lazyProp } from '@bemoje/decorators'

class Config {
  @lazyProp
  get expensiveValue() {
    console.log('Computing...')
    return Array.from({ length: 1000 }, (_, i) => i * i)
  }
}

const config = new Config()
config.expensiveValue // logs 'Computing...', returns array
config.expensiveValue // returns cached array (no recomputation)

Lazy Properties with Expiry

Cache values with automatic timeout-based invalidation:

import { lazyProp } from '@bemoje/decorators'

class DataService {
  @lazyProp('5 min') // re-fetches after 5 minutes
  get cachedData() {
    return fetchFromDatabase()
  }

  @lazyProp(30000) // re-fetches after 30 seconds
  get frequentlyUpdated() {
    return getLatestMetrics()
  }
}

Sync Memoization

Cache method results based on arguments:

import { memoizeSync } from '@bemoje/decorators'

class MathService {
  @memoizeSync()
  fibonacci(n: number): number {
    if (n <= 1) return n
    return this.fibonacci(n - 1) + this.fibonacci(n - 2)
  }
}

const svc = new MathService()
svc.fibonacci(40) // computed once, cached for subsequent calls

Async Memoization

Cache async method results with optional TTL:

import { memoizeAsync } from '@bemoje/decorators'

class ApiClient {
  @memoizeAsync('10 min')
  async fetchUser(id: string) {
    const res = await fetch(`/api/users/${id}`)
    return res.json()
  }
}

const client = new ApiClient()
await client.fetchUser('123') // fetches from API
await client.fetchUser('123') // returns cached result