Hello, and welcome back! Last time, we successfully made our first Whisper API request to transcribe audio using OpenAI's service. Armed with that knowledge, we'll now build resilience into your transcription system by implementing error handling and adding retries. This lesson expands on your current skills to ensure that even when errors occur, your application remains robust and continues running smoothly.

In this lesson, you'll learn how to use TypeScript higher-order functions to wrap function calls for error handling, implement retries for more reliable API requests, and deepen your understanding of adding functionality to functions. These concepts are critical when interacting with APIs, since network issues or server timeouts shouldn't derail your entire application.

In real-world applications, errors can arise for various reasons — such as network interruptions, server downtimes, or temporary glitches. Instead of terminating the process, implementing retries allows the system to recover gracefully.

In TypeScript, we can achieve this using higher-order functions. A higher-order function is a function that takes one or more functions as arguments and/or returns a function. This pattern allows us to wrap existing functions with additional behavior — such as logging, retries, or authentication checks — without modifying the original function itself.

Let's define a higher-order function called withRetry that handles retries for any asynchronous function:

Here's how it works step by step:

1. Parameters: fn is the function to wrap. You can customize how many times to retry (maxRetries) and how long to wait between attempts (delay in ms).

2. Execution and Retry. The returned wrapper attempts to execute fn in a try/catch loop. On error, it logs the failure, waits, and retries.

3. Failure Exit. If the maximum retries are exhausted, the error is re-thrown so the calling code can handle it.

Included the following explanation at the end of the paragraph:

The line fn: (...args: any[]) => Promise<T> means we're accepting a function (fn) that can take any number of arguments (thanks to the ...args rest parameter) and returns a Promise. We use Promise<T> because the function we're wrapping is asynchronous and we want to preserve that async behavior.

Similarly, return async (...args: any[]): Promise<T> => { ... } defines the function we return from withRetry. It also takes any number of arguments and returns a , allowing us to the original function inside it. This pattern gives us flexibility to retry any async function, regardless of how many parameters it needs.

Now, let's apply our retry logic to the transcription function:

• The transcribeWithoutRetry function handles the actual API call.
• The withRetry wrapper ensures that transient errors are retried up to three times with a 5-second delay between attempts.
• If all retries fail, the final error is caught and logged by the main function.

Sometimes, not all errors should be retried. For instance, authentication errors are not recoverable without user input. To handle such cases, we can enhance our logic using withSmartRetry:

This version adds a shouldRetry function to filter errors. You can implement custom logic (e.g., avoid retrying on invalid tokens, file format issues, or permission errors).

In this lesson, we've enhanced your transcription system by implementing error handling and retry mechanisms using TypeScript higher-order functions.

You learned to:

• Write reusable wrappers (withRetry, withSmartRetry) that handle transient failures.
• Wrap transcription logic to ensure resilience during OpenAI API interactions.
• Customize retry behavior using conditional logic to avoid retrying on unrecoverable errors.

These patterns are essential for robust, production-grade applications. They not only reduce failure rates but also improve user experience by gracefully handling temporary issues — all without changing the core logic of your business functions.