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Oct 5, 2021
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42 changes: 42 additions & 0 deletions Cache/Memoize.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
/**
* Memoize
*
* From [Wikipedia](https://en.wikipedia.org/wiki/Memoization),
* memoization is an optimization technique
* used primarily to speed up computer programs,
* by storing the results of expensive function calls
* and returning the cached result when the same inputs occur again
*
* This function is a first class objects,
* 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
* @returns {Function} Memoized function
*/
export const memoize = (func) => {
// Initialization of a slot to store the function result
const cache = {}

return (...args) => {
// Retrieving the first argument of the function
const [arg] = args

/**
* Checks if the argument is already present in the cache,
* then return the associated value / result
*/
if (arg in cache) {
return cache[arg]
}

/**
* If the argument is not yet present in the cache,
* execute original function and save its value / result in cache,
* finally return it
*/
const result = func(arg)
cache[arg] = result
return result
}
}
37 changes: 37 additions & 0 deletions Cache/test/Memoize.test.js
Original file line number Diff line number Diff line change
@@ -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(3628800)
})
})