What is it

Function expects a passing of async_method.

• Any async function that will take an argument.

cache variable is a cache recording registry.

• Each record consists of key that is a stringified version of arguments passed to the method.
• value that is a Promise (not yet awaited) that calls the async function with the given arguments.

We are caching the promise returned by the method, not the final value.

function memoize(async_method) {
  let cache = {};
  
  return async function() {
    let args = JSON.stringify(arguments);
    
    // store promise (before awaiting) as value
    cache[args] = cache[args] || async_method.apply(this, arguments);

    return cache[args];
  };
}

How to use it:

const getSomeDataMemoized = memoize(async function() {
  return await fetch("/api/someRoute", {
    method: "GET",
  });
});

const getAnotherRequestMemoized = memoize(async function() {
  return await fetch("/api/otherRequest", {
    method: "GET",
  });
});

const materFunction = memoize(async function() {
  const [result1, result2] = await Promise.all([
    getSomeDataMemoized(), getAnotherRequestMemoized()
  ]);
  
  return result1;
});