You are developing an application that continuously checks for incoming messages and processes them immediately. Which looping structure could be used to handle message checking and processing, and what considerations should be taken into account for performance and user experience?
- for...of loop with asynchronous functions
- setInterval with an event-driven approach
- do-while loop with synchronous functions
- setTimeout with an event-driven approach and callbacks
Using setInterval with an event-driven approach is a suitable choice for continuously checking and processing incoming messages. This approach allows you to define a specific interval for checking messages, balancing performance and user experience. Options like for...of with asynchronous functions might not provide consistent timing, and do-while with synchronous functions could lead to performance issues. setTimeout with callbacks is more suitable for one-time delays.
In JavaScript, when a function is defined inside another function, the inner function has access to the ________ of the outer function due to lexical scoping.
- Variables
- Properties
- Methods
- Parameters
In JavaScript, when a function is defined inside another function, the inner function has access to the variables of the outer function due to lexical scoping. Lexical scoping means that the inner function "remembers" the scope in which it was created, allowing it to access and manipulate variables defined in the outer function. This behavior is one of the fundamental aspects of closures in JavaScript.
Which object represents the response to a request?
- request
- httpRequest
- response
- httpResponse
In the context of making HTTP requests, the object that represents the response to a request is simply called the "response" object. This object contains information about the response, including the HTTP status code, headers, and the response body. Developers can access and manipulate this object when working with web APIs or performing HTTP requests in JavaScript.
Which HTTP status code indicates that the server has successfully processed the request but there is no content to send in the response?
- 200 OK
- 204 No Content
- 404 Not Found
- 500 Internal Server Error
The HTTP status code 204 No Content indicates that the server has successfully processed the request, but there is no data to send back in the response body. It is often used when a request doesn't return any content, like in a successful DELETE request or when fetching data that hasn't changed since the last request.
What will be the default behavior of an AJAX call regarding page reload?
- Page does not reload
- Page reloads
- It depends on the HTTP method
- Page refreshes after a delay
By default, an AJAX (Asynchronous JavaScript and XML) call does not trigger a page reload. AJAX requests allow you to retrieve or send data to the server without reloading the entire web page. This behavior is essential for creating interactive web applications that update content dynamically without disrupting the user experience.
Closures can help in creating data _________ by providing data privacy and are used to create factory functions for building similar objects.
- Encapsulation
- Abstraction
- Inheritance
- Isolation
Closures provide a form of data isolation, which is essential for data privacy in JavaScript. They allow you to encapsulate data within a function's scope, making it inaccessible from the outside, thus achieving data isolation and privacy. This concept is often used in creating factory functions.
You're working on a project where you have to fetch data from an API and display it on a webpage without refreshing it. Which technology would be most suitable for this?
- WebSockets
- Fetch API
- REST API
- GraphQL
The Fetch API is commonly used for making asynchronous network requests, including fetching data from APIs and updating web pages without refreshing. While WebSockets are used for real-time communication, REST and GraphQL are architectural approaches, not technologies.
How do arrow functions affect the call stack and debugging in JavaScript?
- They have no impact on the call stack.
- They add an extra layer to the call stack.
- They make debugging more straightforward.
- They can cause stack overflow errors.
Arrow functions have no impact on the call stack, as they do not create their own execution context or call themselves recursively. This means they don't contribute to the call stack depth, making it easier to avoid stack overflow errors in certain cases. However, it's essential to understand how this behavior can affect debugging and performance when using arrow functions in JavaScript.
Which method returns the first element that matches a CSS selector(s)?
- querySelectorAll()
- selectElementByCSS()
- getElementBySelector()
- getElementsByClassName()
The querySelectorAll() method is used to return all elements in the document that match a specified CSS selector. However, if you want to retrieve only the first matching element, you can use the querySelector() method. The other options are not standard JavaScript methods for selecting elements by CSS selector.
How can you use a for...in loop to access the properties of an object?
- By using the index values.
- By using the Object.keys() method.
- By using the Object.entries() method.
- By using the Object.getOwnPropertyNames() method.
A for...in loop is used to iterate over the enumerable properties of an object. To access the properties of an object, you can use the Object.keys() method, which returns an array of the object's own enumerable property names. This allows you to loop through the keys (property names) of the object and access their corresponding values. It's a safer and more controlled way to work with object properties than a simple for...in loop.