Function memoize

Create a new Function that returns the memoized results of a Function. The key for the lookup cache is determined by the keyExtractor Function.

An optional Map instance can be provided to be used as cache. This allows for example to prepopulate the cache, or to force recomputation of some values by removing their corresponding keys. If no instance is provided an empty Map will be created.

Remarks

The memoized function should be a pure function, because else side effects will only be executed once for each cached key.

Example

Memoize an expensive function

const expensiveFunction = (a, b) => a + b;
const keyExtractor = (a, b) => `${a}_${b}`;

const memoizedFunction = memoize(expensiveFunction, keyExtractor);

const result = memoizedFunction(2, 3);
console.log(result); // 5

Example

Provide an initial cache restored from database

const restoredCacheFromDatabase = new Map([["a", 1], ["ab", 2]]);
const expensiveFunction = (s) => s.length;
const keyExtractor = (s) => s;

const memoizedFunction = memoize(expensiveFunction, keyExtractor, restoredCacheFromDatabase);

const result = memoizedFunction("ab");
console.log(result); // 2

Example

Clear cache after 5 seconds

const cache = new Map();
const expensiveFunction = (s) => s.length;
const keyExtractor = (s) => s;

const memoizedFunction = memoize(expensiveFunction, keyExtractor, cache);

// ... fill the cache

setTimeout(() => {
  cache.clear();
}, 5000);

Returns

the memoized result