merge: Added explicit cache feature & optional parameter (#941)

Cache/Memoize.js

@@ -10,12 +10,10 @@
  * which lets us use it as [Higher-Order Function](https://eloquentjavascript.net/05_higher_order.html)
  * and return another function
  * @param {Function} func Original function
+ * @param {Map} cache - it's receive any cache DS which have get, set & has method
  * @returns {Function} Memoized function
  */
-const memoize = (func) => {
-  // Initialization of a slot to store the function result by arguments as a key in Hash Map
-  const cache = new Map()
-
+const memoize = (func, cache = new Map()) => {
   const jsonReplacer = (_, value) => {
     if (value instanceof Set) { // if the value is Set it's converted to Array cause JSON.stringify can't convert Set
       return [...value]

Cache/test/Memoize.test.js

@@ -2,6 +2,7 @@ import { memoize } from '../Memoize'
 import { union } from './cacheTest'
 import { fibonacci } from '../../Dynamic-Programming/FibonacciNumber'
 import { factorial } from '../../Recursive/Factorial'
+import LFUCache from '../LFUCache'
 
 const multipleFactorials = (arr) => arr.map(factorial)
 
@@ -51,4 +52,17 @@ describe('Testing Memoize', () => {
     expect(memoUnion(...inputs)).toEqual(new Set([1, 2, 3, 4, 5, 6]))
     expect(memoUnion(...inputs)).toEqual(union(...inputs))
   })
+
+  it('Testing with explicit cache -> LFUCache', () => {
+    const LFU = new LFUCache(2)
+
+    const memoizeFibonacci = memoize(fibonacci, LFU) // added LFU cache explicitly
+    const fibOfFiveHundred = memoizeFibonacci(500)
+    const fibOfOneHundred = memoizeFibonacci(100)
+
+    expect(memoizeFibonacci(500)).toBe(fibOfFiveHundred)
+    expect(memoizeFibonacci(100)).toBe(fibOfOneHundred)
+
+    expect(LFU.leastFrequency).toBe(2)
+  })
 })