How does the event loop manage asynchronous operations in JavaScript?
- It uses multithreading to execute multiple tasks concurrently.
- It queues asynchronous tasks and processes them sequentially.
- It creates separate threads for each asynchronous task.
- It uses callbacks to handle asynchronous tasks.
The event loop in JavaScript manages asynchronous operations by queuing them and processing them sequentially. This approach ensures that JavaScript remains single-threaded, preventing concurrency issues and making it non-blocking. This mechanism is crucial for handling I/O operations efficiently and maintaining a responsive user interface.
Which data type is NOT available in JavaScript?
- Symbol
- Float
- String
- Array
JavaScript supports a wide range of data types, including numbers, strings, symbols, and arrays. However, "Float" is not a distinct data type in JavaScript; instead, it uses the "number" data type to represent both integers and floating-point numbers. Symbols are used for creating unique identifiers, strings store text, and arrays are used to store collections of values.
A function declaration is hoisted to the top of the ________ in which it was defined.
- Scope
- Block
- Function
- Statement
A function declaration is hoisted to the top of the function in which it was defined. This means you can use a function before declaring it in your code, but it's important to understand the implications of hoisting for variable scoping.
The method _______ is used to sort the elements of an array.
- sort()
- splice()
- split()
- reduce()
The correct method is sort(). JavaScript arrays have a built-in sort() method that is used to sort the elements of an array in ascending order by default. You can also provide a compare function to customize the sorting behavior. For example, myArray.sort((a, b) => a - b) sorts the array numerically.
You're refactoring your code to improve performance and notice a function that returns another function, accessing variables outside of its own scope. What specific JavaScript concept should you consider when optimizing this code section?
- Function Closures
- Function Prototypes
- Event Bubbling
- AJAX (Asynchronous JavaScript and XML)
When optimizing code that returns a function and accesses variables outside of its own scope, you should consider the concept of function closures. Function closures allow an inner function to "remember" and access variables from its containing (parent) function's scope even after the parent function has finished executing. This can be useful for encapsulating state and optimizing code.
How can you handle exceptions within a "for" loop to prevent it from being terminated prematurely?
- By wrapping the entire loop in a try-catch block
- By using the "continue" statement
- By adding a "finally" block after the loop
- By setting a maximum execution time for the loop
To handle exceptions within a "for" loop, you can wrap the entire loop in a try-catch block. This allows you to catch and handle exceptions that occur during the loop's execution, preventing it from being terminated prematurely. The other options do not directly address exception handling within the loop.
How does an arrow function handle the "this" keyword differently than regular functions?
- Arrow functions inherit the "this" value from their containing scope.
- Arrow functions have their own "this" context.
- Arrow functions automatically bind "this" to the global object.
- Arrow functions can't use "this" keyword.
Arrow functions behave differently from regular functions when it comes to the "this" keyword. They inherit the "this" value from their containing lexical (surrounding) scope, while regular functions have their "this" determined by how they are called. This behavior can be advantageous in certain situations.
The _________ method is used to bind an object context to a function and is called immediately.
- Bind
- Apply
- Call
- Invoke
The "call" method in JavaScript is used to bind an object's context to a function and is called immediately. It allows you to specify the value of "this" explicitly when invoking a function, along with any additional arguments you want to pass to the function.
How can you select all
elements within a specific parent element?
- document.getElementsByTagName('p')
- document.select('p')
- document.querySelectorAll('p')
- parentElement.querySelectorAll('p')
To select all
elements within a specific parent element, you can use the querySelectorAll() method on the parent element. This method allows you to specify the CSS selector within the context of the parent element, ensuring that only
elements within that parent are selected. The other options are incorrect for this purpose.
How can you prevent script injection attacks when dynamically modifying element content with user input?
- Use the innerText property to set the content.
- Use the innerHTML property to set the content.
- Use a library like jQuery to sanitize input data.
- Use textContent property to set the content.
To prevent script injection attacks, it's crucial to use the textContent property to set content dynamically. Unlike innerHTML, which parses and executes scripts, textContent treats input as plain text, reducing the risk of script injection. Using libraries may help but doesn't guarantee security. innerText has limited browser support.