Memoization in JavaScript: Speeding up Your Applications

Memoization is a technique that allows you to significantly improve the performance of your JavaScript applications. While this technique is not unique to JavaScript, this article will focus on providing JavaScript examples.

In simple terms, memoization involves storing the result of a function call and returning it when the function is called again with the same input. It can be thought of as caching for functions.

So why is memoization useful? Well, imagine you have a function that takes a second to execute. By using memoization, you can reduce the execution time to just a few milliseconds, resulting in a noticeable performance gain.

However, there is a catch. Memoization only works if the function is pure, meaning that calling the function with the same set of arguments will always produce the same output. Operations such as database queries, network requests, and writing to files are not suitable for memoization because they are impure. In these cases, you’ll need to find alternative optimization techniques or accept the inefficiency that accompanies them.

Let’s take a look at an example:

// Calculate the factorial of num
const fact = num => {
  if (!fact.cache) {
    fact.cache = {};
  }
  if (fact.cache[num] !== undefined) {
    console.log(num + ' cached');
    return fact.cache[num];
  } else {
    console.log(num + ' not cached');
  }
  
  fact.cache[num] = num === 0 ? 1 : num * fact(num - 1);
  return fact.cache[num];
};

In this example, we calculate the factorial of a number. The first time fact() is called, it creates a cache object property on itself to store the result of the calculation. On subsequent calls, if the result is found in the cache object, it is returned without performing the calculation again.

You can try running this example on CodePen to see how it works.

If modifying the function itself is not an option, there are libraries available that provide memoization functionality for any pure function. One such library is fast-memoize. Additionally, if you are a fan of Lodash, it offers a memoize() method that you can use.

Memoization is a powerful optimization technique that can significantly improve the performance of your JavaScript applications. By storing and reusing function results, you can avoid unnecessary computations and achieve faster execution times.

Tags: JavaScript, memoization, optimization