kim-nguyenkhn / memoize

Simple demonstration on memoization in JavaScript.

memoize

Simple demonstration on memoization in JavaScript.

Heavily inspired by Daniel Brain's medium post.

How to run

node index.js

Running the code will calculate the Fibonacci number of 123456, repeat this calculation 10000 times, and pop out the run-time in milliseconds.

The first number represents the un-memoized call, with the second being the memoized call.

What is memoization?

I'll borrow this great definition from Divyanshu Maithani's article:

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.

In other words, memoization is a way to store results into a cache and retrieve those cached results.

The benefit becomes obvious as function calls get more expensive - why would you want to repeat expensive calls if you already have the result from an earlier call?

Memoization function

let memoize = function(method) {
  let cache = {};

  return async function() {
    let args = JSON.stringify(arguments);
    cache[args] = cache[args] || method.apply(this, arguments);
    return cache[args];
  };
};

This function turns any function into a memoized one.

If the memoized function is called twice with the same arguments, it will return the same cached value the 2nd time.

It's important to note that the promise is being cached, and not the final value.