From 028e098b63bbf8f5ed46eedbaa38d09c28202db4 Mon Sep 17 00:00:00 2001
From: Damien Chazoule <damien.chazoule@gmail.com>
Date: Mon, 4 Oct 2021 13:40:17 +0200
Subject: [PATCH] Feat: Added Memoize Func

---
 Cache/Memoize.js                | 29 ++++++++++++++++++++++++++
 Cache/__tests__/Memoize.test.js | 37 +++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 Cache/Memoize.js
 create mode 100644 Cache/__tests__/Memoize.test.js

diff --git a/Cache/Memoize.js b/Cache/Memoize.js
new file mode 100644
index 000000000..932b6187c
--- /dev/null
+++ b/Cache/Memoize.js
@@ -0,0 +1,29 @@
+/**
+ * Memoize
+ * @param {Function} fn
+ * @returns
+ */
+export const memoize = (func) => {
+  // eslint-disable-next-line no-console
+  console.log(`Creating cache for function '${func.name}'`)
+
+  const cache = {}
+
+  return (...args) => {
+    const [arg] = args
+
+    if (arg in cache) {
+      // eslint-disable-next-line no-console
+      console.log(`Reading cache with argument ${arg}`)
+
+      return cache[arg]
+    }
+
+    // eslint-disable-next-line no-console
+    console.log(`Updating cache with argument ${arg}`)
+
+    const result = func(arg)
+    cache[arg] = result
+    return result
+  }
+}
diff --git a/Cache/__tests__/Memoize.test.js b/Cache/__tests__/Memoize.test.js
new file mode 100644
index 000000000..74f3f5762
--- /dev/null
+++ b/Cache/__tests__/Memoize.test.js
@@ -0,0 +1,37 @@
+import { memoize } from '../Memoize'
+
+const fibonacci = (n) => {
+  if (n < 2) {
+    return n
+  }
+
+  return fibonacci(n - 2) + fibonacci(n - 1)
+}
+
+const factorial = (n) => {
+  if (n === 0) {
+    return 1
+  }
+
+  return n * factorial(n - 1)
+}
+
+describe('memoize', () => {
+  it('expects the fibonacci function to use the cache on the second call', () => {
+    const memoFibonacci = memoize(fibonacci)
+
+    expect(memoFibonacci(5)).toEqual(fibonacci(5))
+    expect(memoFibonacci(5)).toEqual(5)
+    expect(memoFibonacci(10)).toEqual(fibonacci(10))
+    expect(memoFibonacci(10)).toEqual(55)
+  })
+
+  it('expects the factorial function to use the cache on the second call', () => {
+    const memoFactorial = memoize(factorial)
+
+    expect(memoFactorial(5)).toEqual(factorial(5))
+    expect(memoFactorial(5)).toEqual(120)
+    expect(memoFactorial(10)).toEqual(factorial(10))
+    expect(memoFactorial(10)).toEqual(3_628_800)
+  })
+})