JS: Memoization example

sqrt-memoization.js

function memoize(fn) {
  return function() {
    const args = Array.prototype.slice.call(arguments);
    fn.cache = fn.cache || {};
    return fn.cache[args]
      ? fn.cache[args]
      : (fn.cache[args] = fn.apply(this, args));
  };
}

function sleep(timeout) {
  return new Promise(resolve => setTimeout(resolve, timeout));
}

async function sqrt(num) {
  await sleep(1000); // fake background worker
  return Math.sqrt(num);
}

// No memoization
async function app1() {
  console.log(await sqrt(3));
  console.log(await sqrt(3));
  console.log(await sqrt(3));
}

// Applying memoization
async function app2() {
  const memoizedSqrt = memoize(sqrt);
  console.log(await memoizedSqrt(9));
  console.log(await memoizedSqrt(9));
  console.log(await memoizedSqrt(9));
}

app1();
app2();