How does error handling differ in async/await compared to traditional promise-based approaches?
- Both handle errors in the same way
- Async/await uses try...catch for error handling
- Promises use try...catch for error handling
- Async/await relies on callback functions
In async/await, errors are handled using the familiar try...catch block, making it easier to write and read asynchronous code. This improves the debugging experience compared to chaining .then() and .catch() in promise chains.
What happens when you add duplicate elements to a Set?
- Ignored, Overwritten, Error, Concatenated
- Overwritten, Ignored, Concatenated, Error
- Concatenated, Overwritten, Ignored, Error
- Ignored, Concatenated, Error, Overwritten
When you add duplicate elements to a Set in JavaScript, they are ignored. Unlike Arrays or Objects, Sets only allow unique values, ensuring that the Set contains only distinct elements. Adding a duplicate element does not result in an error, and the Set remains unchanged.
To prevent infinite recursion, it is important to define a __________ that stops the recursion.
- Base case
- Recursive case
- Break statement
- Counter variable
In recursive functions, a base case is crucial to terminate the recursion. It is the condition that, when met, stops the function from calling itself endlessly.
In the map method, what happens if the callback function doesn't return any value?
- It throws an error
- It returns undefined for each element
- It skips the current element in the resulting array
- It returns an array of null values
If the callback function in the map method doesn't return any value (implicitly or explicitly), each corresponding element in the resulting array will have the value undefined. It's essential to ensure that the callback function produces meaningful output to avoid unexpected results.
What happens if super() is called multiple times in a constructor?
- It triggers an error
- It executes the parent constructor multiple times
- Only the last call is effective
- It has no effect
Calling super() multiple times in a constructor is an error. It must be called once and must be the first statement in the constructor. Subsequent calls to super() would result in an error.
What types of values can be added to a WeakSet?
- Only objects can be added.
- Any data type, including primitives, can be added.
- Only functions can be added.
- Only arrays can be added.
WeakSets exclusively allow objects, emphasizing their use for storing unique object references and aiding in scenarios like memory management.
Can a pure function modify a global variable?
- Yes
- No
- It depends
- Only if it's a constant variable
No, a pure function should not modify global variables or any external state. It should only depend on its input parameters to produce the output and should not have side effects. Modifying global variables violates the principles of pure functions.
In a web application, how can higher-order functions be used to enhance event handling?
- reduce
- map
- forEach
- filter
The correct option is forEach. forEach is commonly used for iterating over elements in an array, making it suitable for enhancing event handling in a web application where actions need to be performed on each element.
Consider a scenario where you need to add common functionalities to several unrelated classes in ES6. How would mixins and composition address this requirement?
- By using inheritance to create a base class with common functionalities.
- By creating separate mixins for each functionality and applying them to the unrelated classes.
- By directly adding methods to each unrelated class.
- By creating a utility class that encapsulates the common functionalities and using composition to add it to each class.
Mixins and composition can address this requirement by creating separate mixins for each functionality and applying them to the unrelated classes. This promotes code reuse without the need for inheritance.
If you're building a library with a primary functionality and several auxiliary functions, how would you organize your exports?
- Using named exports for each auxiliary function
- Using a default export for the primary functionality and named exports for auxiliary functions
- Using a default export for each function, combining primary and auxiliary functionalities
- Using a single named export for the entire library
When building a library, using a default export for the main functionality and named exports for auxiliary functions is a common practice. This way, consumers can import only the specific functionalities they need, optimizing bundle size and avoiding unnecessary code.