A try/catch block inside an async function catches both synchronous and ________ errors.
- Promise
- Callback
- Asynchronous
- Await
A try/catch block inside an async function can catch both synchronous errors (those that occur in the synchronous part of the code) and asynchronous errors (those that occur in asynchronous operations like Promises). This ensures robust error handling in async functions.
The ________ method is a special method for creating and initializing objects created within a class.
- constructor
- initialize
- create
- new
In ES6 classes, the constructor method is a special method used for creating and initializing objects within the class. It is automatically called when an object is instantiated from the class.
Consider a web application that needs to fetch data in chunks from the server. How would a generator function improve the handling of these data requests?
- Facilitates lazy loading of data
- Improves network latency
- Enables synchronous requests
- Enhances browser caching
Generator functions enable lazy loading of data, allowing you to fetch data in chunks on demand. This is particularly useful in web applications where you can fetch only the required data, improving efficiency and reducing unnecessary data transfers.
In a function that calculates the sum of an array, how would the use of let and const impact the function's readability and bug prevention?
- Use of let would enhance readability, and const would prevent bugs
- Use of const would enhance readability, and let would prevent bugs
- Use of let and const together would enhance both readability and bug prevention
- It doesn't matter, let and const behave the same way in this context
Using const for variables that shouldn't be reassigned increases code readability, and using let for variables that can be reassigned helps prevent accidental bugs.
Can composition in ES6 be used to combine multiple behaviors into a single object?
- Yes, by using the extends keyword
- No, composition is not supported in ES6
- Yes, by using the compose function
- Yes, by using the inherit keyword
Composition in ES6 can indeed be used to combine multiple behaviors into a single object. The compose function or pattern involves combining different functions or objects to create a new, more complex one. This approach enhances modularity and allows for the creation of flexible and reusable code.
What is the primary advantage of using composition over inheritance in ES6?
- Code Reusability
- Tight Coupling
- Polymorphism
- Encapsulation
In ES6, composition refers to combining simpler functions or objects to create more complex ones. The primary advantage is improved code reusability and flexibility, as it avoids the issues associated with tight coupling in inheritance. Composition promotes a more modular and maintainable code structure, allowing for better adaptability to changes.
The __________ keyword is used for creating getter methods in an ES6 class.
- Set
- Get
- Define
- Getter
In ES6 classes, the get keyword is used to create getter methods. Getter methods allow you to retrieve the value of an object's property. When a getter method is defined using the get keyword, it is called without the need for parentheses, providing a more natural and property-like syntax when accessing the property.
The method Symbol.for(__________) is used to create Symbols that are __________ across different scopes.
- globalKey'
- sharedKey'
- scopedKey'
- localKey'
Symbol.for() is used to create symbols that are shared across different scopes. It searches for an existing symbol with the given key and returns it if found; otherwise, it creates a new one. Example: const sharedSymbol = Symbol.for('sharedKey');
In an event handler inside a React class component, what implications does using an arrow function have compared to a traditional function?
- No difference
- Better performance
- Avoid using arrow functions
- Avoid using traditional functions
Using an arrow function in a React class component's event handler can lead to better performance, as it avoids the need to bind "this" explicitly. However, it's essential to be cautious about potential memory leaks in certain scenarios.
How does the extends keyword function in class inheritance in ES6?
- It creates a copy of the parent class
- It allows a class to inherit from multiple classes
- It creates a subclass that inherits from a specified class
- It is used to declare a private class member
In ES6, the extends keyword is used to create a subclass that inherits from a specified class. The subclass can then access the properties and methods of the parent class. This facilitates the concept of class inheritance in JavaScript.