Debugging Asynchronous Code: Callbacks, Promises, and Async/Await Quiz Quiz

Delve into core techniques for handling and troubleshooting asynchronous code using callbacks, promises, and async/await. This quiz enhances your understanding of error handling, data flow, and common pitfalls in asynchronous programming.

1. Identifying Callback Problems

   In a situation where multiple nested callbacks result in messy and hard-to-follow code, what is this commonly referred to?

   1. Callback Hell
   2. Event Loop Tunnel
   3. Async Trap
   4. Promise Stack

   Explanation: The correct term for deeply nested callbacks making code difficult to read and maintain is 'Callback Hell.' 'Promise Stack' and 'Async Trap' are not standard terms in asynchronous programming. 'Event Loop Tunnel' also does not describe this phenomenon. Only 'Callback Hell' precisely matches the described problem and is widely recognized.

2. Promise Error Handling

   Consider the following promise: promise.then(doSomething).catch(doError). What happens if doSomething throws an error?

   1. Execution stops with an uncaught error
   2. doError will be called
   3. The promise is resolved with undefined
   4. doSomething is retried automatically

   Explanation: If doSomething throws an error inside .then, the promise transitions to a rejected state, and .catch executes doError. 'Execution stops with an uncaught error' is incorrect because the error is caught by .catch. 'doSomething is retried automatically' does not occur; errors are not retried by default. 'The promise is resolved with undefined' is not accurate because an error leads to rejection, not resolution.

3. Async/Await Syntax Clarity

   Which keyword must be used before a function definition to allow the use of 'await' inside that function?

   1. promise
   2. defer
   3. await
   4. async

   Explanation: Placing the 'async' keyword before a function enables the use of 'await' within that function. Using 'await' or 'promise' before the function doesn't enable this functionality, and 'defer' has no special meaning in this context. Only 'async' is recognized by the language to provide asynchronous capabilities.

4. Common Pitfall with Promises

   Given 'return fetch(url).then(res =u003E res.json())', what is a common mistake if you forget to return in the arrow function?

   1. The promise never settles
   2. A syntax error is thrown
   3. The resolved value becomes undefined
   4. It causes an infinite loop

   Explanation: If you omit the return statement in the arrow function, the resolved value will be undefined because nothing is passed to the next 'then'. 'The promise never settles' is incorrect because the promise still resolves, just with undefined. There is no syntax error, and no infinite loop is created. The missing return specifically results in undefined as the value.

5. Detecting Asynchronous Race Conditions

   Suppose two asynchronous functions update the same variable without coordination. What kind of bug is most likely to occur?

   1. Time Overflow
   2. Loopback Error
   3. Promise Leak
   4. Race Condition

   Explanation: When multiple asynchronous operations update shared state without proper control, a race condition can occur, leading to unpredictable results. 'Time Overflow' and 'Loopback Error' are unrelated to this scenario. 'Promise Leak' refers to unhandled promises, not conflicting data updates. Therefore, 'Race Condition' best describes the likely issue.