Usage

const calls: number[] = [];

const fib = memo((x: number) => {
  calls.push(x);
  return x < 2 ? x : fib(x - 1) + fib(x - 2);
});

fib(10); // 55
fib(10); // 55 (calls === [10])
fib(11); // 89 (calls === [10, 11])

Installation

CLI

npx atmx add helper memo

Manually

Copy and paste the following method into @/utils/helpers/memo.ts:

type Cache<T> = Record<string, { exp: number | null; value: T }>;

function memoize<TArgs extends any[], TResult>(
cache: Cache<TResult>,
func: (...args: TArgs) => TResult,
keyFunc: ((...args: TArgs) => string) | null,
ttl: number | null,
) {
return function callWithMemo(...args: any): TResult {
const key = keyFunc ? keyFunc(...args) : JSON.stringify({ args });
const existing = cache[key];
if (existing !== undefined) {
  if (!existing.exp) {
    return existing.value;
  }
  if (existing.exp > new Date().getTime()) {
    return existing.value;
  }
}
const result = func(...args);
cache[key] = {
  exp: ttl ? new Date().getTime() + ttl : null,
  value: result,
};
return result;
};
}

export interface MemoOptions<TArgs extends any[]> {
key?: (...args: TArgs) => string;
ttl?: number;
}

/**
* Creates a memoized function. The returned function will only
* execute the source function when no value has previously been
* computed. If a ttl (milliseconds) is given previously computed
* values will be checked for expiration before being returned.
*
* @example
* const calls: number[] = []
*
* const fib = memo((x: number) => {
*   calls.push(x)
*   return x < 2 ? x : fib(x - 1) + fib(x - 2)
* })
*
* fib(10) // 55
* fib(10) // 55 (calls === [10])
* fib(11) // 89 (calls === [10, 11])
*/
export function memo<TArgs extends any[], TResult>(
func: (...args: TArgs) => TResult,
options: MemoOptions<TArgs> = {},
): (...args: TArgs) => TResult {
return memoize({}, func, options.key ?? null, options.ttl ?? null);
}