Throttling & Debouncing API Requests for Performance

function createApiDebouncer(apiCallFunction, delay = 300) {
  let timeoutId;
  let lastArgs = null;
  let lastThis = null;
  let resolvePromise = null;
  let rejectPromise = null;

  const debounced = function(...args) {
    lastArgs = args;
    lastThis = this;
    
    // Return a new promise for each debounced call
    return new Promise((resolve, reject) => {
      resolvePromise = resolve;
      rejectPromise = reject;

      clearTimeout(timeoutId);
      timeoutId = setTimeout(async () => {
        try {
          const result = await apiCallFunction.apply(lastThis, lastArgs);
          if (resolvePromise) resolvePromise(result);
        } catch (error) {
          if (rejectPromise) rejectPromise(error);
        } finally {
          // Clear references after execution
          resolvePromise = null;
          rejectPromise = null;
          lastArgs = null;
          lastThis = null;
        }
      }, delay);
    });
  };

  // Optional: Add a throttle-like behavior if needed, or keep it pure debounce.
  // For this example, it focuses purely on debouncing the API call.

  return debounced;
}

// Example Usage:
// This example uses a mock API call for demonstration.
// async function searchApi(query) {
//   console.log(`Calling API for: "${query}"`);
//   return new Promise(resolve => setTimeout(() => resolve(`Results for "${query}"`), 500));
// }

// const debouncedSearchApi = createApiDebouncer(searchApi, 500);

// // Simulate fast typing
// // debouncedSearchApi('a').then(console.log);
// // debouncedSearchApi('ap').then(console.log);
// // debouncedSearchApi('app').then(console.log);
// // setTimeout(() => debouncedSearchApi('appl').then(console.log), 300); // 'app' will be ignored
// // setTimeout(() => debouncedSearchApi('apple').then(console.log), 600); // Only 'apple' will trigger API after 500ms delay.
// // The console will show:
// // Calling API for: "apple"
// // Results for "apple"