What is the common problem addressed by using asynchronous code in JavaScript?
- Blocking the main thread
- Memory Leaks
- Code Complexity
- Code Optimization
The common problem addressed by using asynchronous code in JavaScript is the avoidance of blocking the main thread. Blocking the main thread can lead to unresponsive user interfaces, making the application seem slow or frozen. Asynchronous code helps prevent this issue by allowing non-blocking execution of tasks.
You are developing an e-commerce website and want to fetch product details asynchronously to avoid page reloads. Which method might be appropriate for managing successive data retrieval operations in a clean and maintainable manner?
- Promises
- Callbacks
- Async/Await
- Observables
To manage successive data retrieval operations in a clean and maintainable manner, you can use the "Async/Await" approach in JavaScript. Async/Await simplifies asynchronous code and makes it look more like synchronous code, which can significantly enhance code readability and maintainability. It allows you to write asynchronous code in a more sequential style, making it easier to handle multiple asynchronous operations.
Which API allows you to make non-simple requests to another domain in JavaScript, considering the Same-Origin Policy?
- XMLHttpRequest
- JSONP (JSON with Padding)
- CORS (Cross-Origin Resource Sharing)
- WebSocket
CORS (Cross-Origin Resource Sharing) is the API that allows you to make non-simple requests (such as those with custom headers or methods) to another domain in JavaScript while considering the Same-Origin Policy. XMLHttpRequest is an older alternative but has limitations compared to CORS. JSONP is a workaround technique, not an API, and WebSocket is used for full-duplex communication, not for cross-origin requests.
During a job interview, you're asked about the evolution of JavaScript. The interviewer specifically wants to know about a major shift in JavaScript's usage from merely adding interactivity to web pages to being used in server-side programming. What technology or platform brought about this shift?
- Node.js
- Apache Tomcat
- PHP
- Ruby on Rails
JavaScript's major shift into server-side programming was largely enabled by Node.js. Node.js is a runtime environment that allows JavaScript to be executed on the server, making it suitable for building scalable, server-side applications. It revolutionized web development by unifying front-end and back-end languages.
Why might for...of loops be preferred when working with asynchronous code?
- They can be used with any iterable object.
- They automatically handle Promise resolution.
- They are faster than traditional for loops.
- They provide better error handling mechanisms.
For...of loops are preferred when working with asynchronous code because they automatically handle Promise resolution. When you iterate over an iterable that contains Promises, for...of will await each Promise and provide the resolved value, making it more convenient for working with asynchronous operations.
What is the primary difference between while and do-while loops in JavaScript?
- The while loop always executes the code block at least once
- The do-while loop is more efficient
- The while loop is not suitable for iterating over arrays
- The do-while loop doesn't have a condition
The primary difference is that in a while loop, the condition is checked before executing the code block. If the condition is initially false, the code block may never run. In contrast, the do-while loop guarantees that the code block is executed at least once because it checks the condition after executing the block. This makes do-while useful when you want the code to run once before checking the condition.
The ________ operator can be used to compare both value and type in JavaScript.
- Equality (===)
- Assignment (=)
- Identity (==)
- Inequality (!=)
The Equality (===) operator can be used to compare both value and type in JavaScript. It checks if two values are strictly equal, meaning they have the same value and the same data type. The other options, such as Assignment (=) and Identity (==), do not perform strict value and type comparison. Inequality (!=) checks for inequality.
The process of an object inheriting properties and behaviors (methods) from its prototype is known as _________.
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
Inheritance is the process by which an object inherits properties and behaviors (methods) from its prototype or parent object. JavaScript uses a prototype-based inheritance model, where objects inherit from other objects, and this is a fundamental concept in the language.
The ________ method is used to read a Response stream and return it as a blob.
- text()
- json()
- blob()
- arrayBuffer()
The blob() method is used to read a Response stream and return it as a blob object. This is commonly used when dealing with binary data or files. The other options (text(), json(), arrayBuffer()) are used for different types of Response data processing.
You are debugging a web application and notice that a "for" loop is causing the webpage to hang. What could be a potential reason and how might you solve it?
- Infinite Loop
- Excessive DOM Manipulation
- Missing Loop Condition
- Insufficient Memory Allocation
One potential reason for a webpage hang caused by a "for" loop is excessive DOM manipulation within the loop, which can block the main thread. To solve this, consider moving DOM manipulation outside the loop or optimizing the DOM operations. An infinite loop, missing loop condition, or insufficient memory allocation could also cause hangs but are less likely in this context. JavaScript Debugging