-memo-args

README.md

npm i gist:e941ee28eb4e4072ebbe9d696fdfb7af

const { memoArgs, memoLastArgs } = require('memo-args')

memoArgs(func)

memoLastArgs(func)

index.js

'use strict'

function memoArgs (fn) {
  const NONE = {}

  const root = {
    result: NONE,
    byVal: null,
    byRef: null,
  }

  return (...args) => {
    let node = root

    for (let i = 0; i < args.length; ++i) {
      const key = args[i]

      const cache = key === Object(key)
        ? node.byRef || (node.byRef = new WeakMap())
        : node.byVal || (node.byVal = new Map())

      node = cache.get(key)
      if (!node) {
        node = {
          result: NONE,
          byVal: null,
          byRef: null,
        }
        cache.set(key, node)
      }
    }

    if (node.result === NONE) {
      node.result = fn(...args)
    }

    return node.result
  }
}

function memoLastArgs (fn) {
  let lastArgs = [{}]
  let lastResult
  const isSameAsLastArg = (arg, i) => arg === lastArgs[i]

  return (...args) => {
    if (args.length !== lastArgs.length || !args.every(isSameAsLastArg)) {
      lastResult = fn(...args)
      lastArgs = args
    }
    return lastResult
  }
}

module.exports = {
  memoArgs,
  memoLastArgs,
}

package.json

{
  "version": "0.0.1",
  "name": "memo-args"
}