What is the main purpose of an iterable in JavaScript ES6?
- Iterables allow you to represent a sequence of values that can be iterated (looped) over.
- Iterables are used for defining constants in JavaScript.
- Iterables help in creating asynchronous functions.
- Iterables provide a way to declare variables in JavaScript.
In JavaScript ES6, iterables are objects that implement the iterable protocol, allowing them to be looped over using the new for...of loop. They are crucial for working with collections of data, enabling efficient and concise iteration.
In a derived class, if you omit the constructor, JavaScript automatically calls super with _______.
- Arguments of the derived class
- Undefined
- nan
- Arguments of the parent class
If the derived class constructor is omitted, JavaScript implicitly adds one, calling super() with undefined as arguments. This ensures the parent class constructor is invoked.
To handle multiple AJAX requests concurrently and wait for all to complete, use Promise._______.
- all
- race
- any
- chain
To handle multiple AJAX requests concurrently and wait for all to complete, use Promise.all(). This method takes an array of promises and waits until all of them are resolved or any one is rejected.
If you're building a function to fetch user data and then fetch related posts based on that data, how would you structure your Promise chain?
- Nested Promises
- Promise.all()
- Promise.chain()
- Async/Await
You would structure your Promise chain using nested promises. This involves chaining .then() handlers to ensure the sequence of asynchronous operations. This allows you to fetch user data first and then, based on that data, fetch related posts in a structured manner.
To ensure the uniqueness of a Symbol, it is created using Symbol(__________), where the argument is optional.
- key'
- id'
- description'
- optional'
In JavaScript, Symbols are used to create unique identifiers. The argument passed to Symbol() is optional and can be used to provide a description for debugging purposes. Example: const mySymbol = Symbol('This is a description');
ES6 mixins can be seen as an alternative to traditional ___________ in object-oriented programming.
- Inheritance
- Encapsulation
- Polymorphism
- Abstraction
The correct option is Inheritance. ES6 mixins provide an alternative to traditional inheritance in object-oriented programming. With mixins, you can compose functionality from multiple sources without the need for a deep inheritance hierarchy, promoting a more modular and flexible code structure.
In ES6, __________ methods are not enumerable in a class definition.
- static
- prototype
- constructor
- get
In ES6, static methods are not enumerable in a class definition. Static methods are attached to the class itself rather than its instances, and they are not iterated over when enumerating the properties of a class. This distinction is important when dealing with class-related operations.
What is the difference in error handling between then/catch and async/await syntax?
- then/catch is used with synchronous code, and async/await is used with asynchronous code
- then/catch is promise-based, and async/await is generator-based
- then/catch is chaining, and async/await uses try/catch
- then/catch is for handling resolved values, and async/await is for handling rejections
The key difference lies in syntax and structure. then/catch involves chaining promises, while async/await uses a more synchronous and linear try/catch structure. async/await provides a cleaner and more readable way to handle asynchronous operations.
How does error handling differ between traditional callbacks and Promises?
- Callbacks: Handle errors using traditional try-catch blocks.
- Promises: Errors are handled using .catch() method.
- Callbacks: Error handling is scattered, making it harder to manage.
- Promises: Provides a more structured and centralized approach to error handling.
In traditional callbacks, error handling relies on try-catch blocks within each callback, leading to scattered code. Promises offer a cleaner approach with a dedicated .catch() method, providing centralized error handling and making the code more readable and maintainable.
What is the main difference between using XMLHttpRequest and the Fetch API in terms of handling responses?
- Fetch API returns a Promise that resolves with the Response
- XMLHttpRequest directly returns the Response object
- Fetch API uses callbacks for response handling
- XMLHttpRequest handles responses synchronously
The Fetch API returns a Promise that resolves with the Response object, providing a more modern and convenient way to handle responses. XMLHttpRequest, on the other hand, relies on direct access to the Response object without the benefits of Promises.