@naturalcycles/js-lib/dist/decorators/memoSimple.decorator.js

Standard library for universal (browser + Node.js) javascript

// Based on:
// https://github.com/mgechev/memo-decorator/blob/master/index.ts
// http://decodize.com/blog/2012/08/27/javascript-memoization-caching-results-for-better-performance/
// http://inlehmansterms.net/2015/03/01/javascript-memoization/
// https://community.risingstack.com/the-worlds-fastest-javascript-memoization-library/
import { _getTargetMethodSignature } from './decorator.util.js';
import { jsonMemoSerializer, MapMemoCache } from './memo.util.js';
// memoSimple decorator is NOT exported. Only used in benchmarks currently
/**
 * Memoizes the method of the class, so it caches the output and returns the cached version if the "key"
 * of the cache is the same. Key, by defaul, is calculated as `JSON.stringify(...args)`.
 * Cache is stored indefinitely in internal Map.
 * There is more advanced version of memo decorator called `memoCache`.
 *
 * Supports dropping it's cache by calling .dropCache() method of decorated function (useful in unit testing).
 */
export const memoSimple = (opt = {}) => (target, key, descriptor) => {
    if (typeof descriptor.value !== 'function') {
        throw new TypeError('Memoization can be applied only to methods');
    }
    const originalFn = descriptor.value;
    // console.log(`${key} len: ${originalFn.length}`)
    // todo: optimization disabled until "default arg value" use case is solved (see memo.decorator.test.ts)
    /*
  let cache: MemoCache

  // Function with 0 arguments
  if (!originalFn.length) {
    cache = new SingleValueMemoCache()
  } else {
    // Function with > 0 arguments
    cache = new MapMemoCache()
    // cache = new ObjectMemoCache()
  }
   */
    const cache = new MapMemoCache();
    const { logger = console } = opt;
    const keyStr = String(key);
    const methodSignature = _getTargetMethodSignature(target, keyStr);
    descriptor.value = function (...args) {
        const ctx = this;
        const cacheKey = jsonMemoSerializer(args);
        if (cache.has(cacheKey)) {
            return cache.get(cacheKey);
        }
        const res = originalFn.apply(ctx, args);
        cache.set(cacheKey, res);
        return res;
    };
    descriptor.value.dropCache = () => {
        logger.log(`${methodSignature} @memo.dropCache()`);
        cache.clear();
    };
    return descriptor;
};