In a while loop, placing a ________ statement inside the loop can help prevent infinite loops by providing an explicit exit.
- Break
- Continue
- Return
- Stop
In a while loop, placing a "break" statement inside the loop can help prevent infinite loops by providing an explicit exit condition. When a certain condition is met, the "break" statement terminates the loop, allowing you to exit the loop when necessary and avoid infinite iterations.
What is the most common issue developers might face when working with closures and loops together?
- Variable hoisting
- Memory leaks
- Unexpected type coercion
- Event propagation
The most common issue when working with closures and loops together is the creation of memory leaks. This happens when closures inside loops capture references to variables that are continuously changing in the loop, preventing them from being garbage collected, and leading to increased memory consumption. It's crucial to understand and manage these cases to avoid performance problems.
To iterate over the keys in an object, you can use the for...______ loop.
- For...Of
- For...In
- For...Each
- For...While
To iterate over the keys in an object, you can use the for...In loop. This loop is specifically designed for iterating over object properties, allowing you to access each key. The for...Of loop, on the other hand, is used for iterating over the values of iterable objects like arrays.
While developing a web application, you create a class "Product" to hold the basic attributes of products in an e-commerce site. Later, you need to extend the functionality of some products which are on sale without altering the "Product" class. Which design pattern might be most appropriate to implement this additional functionality without modifying the existing "Product" class?
- Decorator Pattern
- Factory Method Pattern
- Singleton Pattern
- Observer Pattern
The Decorator Pattern is a suitable choice in this scenario. It allows you to add new behaviors or functionality (e.g., for products on sale) to existing classes (e.g., "Product") without modifying their structure. This ensures the open-closed principle and maintainability.
How can you implement a while loop without causing a browser to freeze in case of a long-running process?
- Use asynchronous code and setTimeout to break the loop into smaller chunks, allowing the browser to handle other tasks.
- Wrap the loop in a Web Worker to offload it to a separate thread.
- Increase the browser's JavaScript execution stack size to handle long-running loops.
- Use a while loop with a higher timeout value to prevent freezing.
To prevent the browser from freezing during a long-running while loop, you should use asynchronous code and setTimeout to break the loop into smaller chunks. This allows the browser to handle other tasks and prevents the UI from becoming unresponsive. This approach follows the principles of non-blocking and responsive UI in web development.
The _______ method returns a Promise that resolves or rejects as soon as one of the promises in an iterable resolves or rejects, with the value or reason from that promise.
- Promise.race()
- Promise.all()
- Promise.any()
- Promise()
The correct answer is Promise.race(). This method takes an iterable of promises and returns a new promise that settles as soon as one of the input promises resolves or rejects. It's useful when you want to perform an action as soon as any of several asynchronous tasks completes.
The initial version of JavaScript was created in just _________ days.
- 5 days
- 10 days
- 15 days
- 20 days
The initial version of JavaScript was created in just 10 days by Brendan Eich in September 1995. This rapid development was possible due to the language's concise design and its primary purpose of enhancing web page interactivity.
What is "event bubbling" in JavaScript?
- It refers to blowing up events like balloons.
- It is the process of propagating events from child elements to parent elements in the DOM.
- It is the automatic inflation of event objects.
- It is a debugging technique in JavaScript.
"Event bubbling" in JavaScript refers to the process where events that occur on child elements are also propagated or "bubbled" up to their parent elements in the Document Object Model (DOM). This allows you to capture events at higher levels in the DOM hierarchy. Understanding event bubbling is crucial for event handling in JavaScript.
Which design principle is violated if a superclass is aware of its subclasses?
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
When a superclass is aware of its subclasses, it violates the principle of encapsulation. Encapsulation refers to the concept of bundling data and the methods that operate on that data into a single unit or class. In object-oriented programming, classes should not have direct knowledge of their subclasses to promote loose coupling and maintainability. Instead, subclasses should inherit behavior and attributes from the superclass without the superclass needing to know specific details about its subclasses. Violating this principle can lead to code that is less flexible and harder to maintain.
Which method is commonly used to change the text content of an HTML element using JavaScript?
- innerHTML
- setAttribute
- appendChild
- createTextNode
The innerHTML property is commonly used to change the text content of an HTML element using JavaScript. It allows you to set the HTML content of an element, including its text. For example, you can use element.innerHTML = "New Text" to change the content of an element.