Description

In web applications, making repeated API calls to the same endpoint can be inefficient and slow down your app.
To improve performance, developers often use caching — storing responses temporarily and reusing them for a short period.

In this challenge, you’ll create a Cached API Wrapper, a function that caches API responses for a specified duration.
This technique helps reduce redundant network requests and mimics how frameworks and data-fetching libraries optimize performance under the hood.

Your Task

Implement a function cachedApi(timer) that returns another asynchronous function responsible for:

  • Fetching data from the provided URL.
  • Caching the response in memory.
  • Returning cached data if the same URL is requested again before the cache expires.
  • Automatically removing the cache after the given time.
  • Handling errors gracefully.

Method

Function

Description

cachedApi(timer)

Returns a function that wraps fetch with caching logic for the given duration (in ms).

Example

Input

const fetchWithCache = cachedApi(3000);

(async () => {
const data1 = await fetchWithCache("https://jsonplaceholder.typicode.com/todos/1");
console.log("First fetch:", data1);

const data2 = await fetchWithCache("https://jsonplaceholder.typicode.com/todos/1");
console.log("Second fetch (cached):", data2);

setTimeout(async () => {
const data3 = await fetchWithCache("https://jsonplaceholder.typicode.com/todos/1");
console.log("Third fetch (after cache expired):", data3);
}, 4000);
})();

Expected Output

First fetch: { userId: 1, id: 1, title: 'delectus aut autem', completed: false }
Second fetch (cached): { userId: 1, id: 1, title: 'delectus aut autem', completed: false }
Third fetch (after cache expired): { userId: 1, id: 1, title: 'delectus aut autem', completed: false }

Expected Behavior

✅ Caches each API response for the given time
✅ Returns cached result for repeated calls within cache duration
✅ Automatically removes expired cache entries
✅ Handles fetch failures safely

Hints

Hint 1

💡 Use an object or Map to store cached results, using URLs as keys.

Hint 2

Use setTimeout to delete cached data after the given duration.