What is the impact on performance when using a while loop with a condition that evaluates an expression involving function calls?
- High performance impact
- Moderate performance impact
- Low performance impact
- No performance impact
Using a while loop with a condition that involves function calls can have a moderate performance impact. This is because the function calls are evaluated in each iteration, potentially incurring additional processing overhead. It's important to optimize such code to minimize performance issues.
How does the pop() method behave when applied on an empty array?
- It returns undefined and does nothing
- It throws an error
- It removes the last undefined element and returns it
- It returns null
When the pop() method is applied to an empty array in JavaScript, it returns undefined and does nothing to the array. There are no elements to remove, so it simply returns undefined without causing any errors.
Which object is heavily used in AJAX to interact with server-side data?
- XMLHttpRequest
- JSON
- DOM
- Console
XMLHttpRequest is a crucial object used in AJAX (Asynchronous JavaScript and XML) to make HTTP requests to the server and interact with server-side data without requiring a page reload. It allows for asynchronous communication with the server, making web applications more dynamic and responsive.
Considering JavaScript's type coercion, what will be the result of [] == ![]?
- TRUE
- FALSE
- undefined
- Throws an error
JavaScript performs type coercion when comparing values. In this case, the empty array [] is truthy, and ![] evaluates to false. When comparing, the empty array is coerced to false, resulting in true. This behavior can be surprising and is a common gotcha in JavaScript.
How do you ensure that dynamically added elements maintain accessibility features, like ARIA roles?
- Dynamically set ARIA roles using JavaScript after adding the element.
- Browsers automatically assign appropriate ARIA roles to new elements.
- Dynamically added elements cannot have ARIA roles.
- Add ARIA roles directly in the HTML source code.
To ensure that dynamically added elements maintain accessibility features like ARIA roles, you should dynamically set ARIA roles using JavaScript after adding the element. Browsers don't automatically assign ARIA roles, and adding roles directly in the HTML source code isn't dynamic. Option 3 is incorrect.
Unlike traditional functions, arrow functions do not have their own __________.
- this
- arguments
- return
- parameters
Unlike traditional functions, arrow functions do not have their own this binding. In arrow functions, this retains the value of the enclosing lexical context, which makes it useful in cases where you want to maintain the context of the surrounding code, such as in callbacks or when defining functions within functions.
You're debugging a JavaScript application and notice unexpected behavior in the manipulation of an array. The items are not being removed correctly using a method, and it turns out the array is not being modified at all. Which array method might be mistakenly being used?
- pop()
- push()
- splice()
- concat()
The concat() method is often mistakenly used for removing elements from an array because it doesn't modify the original array but returns a new array instead. The correct method for removing elements from an array is splice() or other methods like pop() or shift().
What is "Promise chaining" in JavaScript?
- A method for nesting multiple if statements
- A technique for connecting multiple Promises
- A way to synchronize asynchronous functions
- A method to define variables
"Promise chaining" is a technique in JavaScript where you can connect multiple Promises together. It allows you to execute asynchronous operations sequentially, making code more readable and manageable, especially when dealing with multiple async tasks.
How does the prototype property behave in arrow functions?
- Arrow functions have a prototype property.
- Arrow functions do not have a prototype.
- Arrow functions inherit their prototype.
- Arrow functions override their prototype.
Arrow functions do not have their own this context and do not have a prototype property. Unlike regular functions, arrow functions do not bind their own this value or have a prototype property. This is a key difference to keep in mind when choosing between regular functions and arrow functions in JavaScript.
Consider a situation where you have a switch statement inside a function, and forgetting to include a break statement leads to a bug. How might this bug manifest in the function’s behavior?
- The function might return the value associated with the first matching case, and all subsequent code within the switch block will execute as well.
- The function will throw an error, indicating a missing "break" statement, and won't execute any code within the switch block.
- The function will automatically insert "break" statements at the end of each case, ensuring correct behavior.
- The function will ignore the switch statement and continue executing the code outside of the switch block.
If you forget to include a "break" statement in a switch case, it will lead to a bug where the function may not behave as expected. Instead of stopping after the first matching case, the switch statement will "fall through" to subsequent cases, causing unintended behavior. The correct option is to use a "break" statement to exit the switch block after handling a case. JavaScript doesn't automatically insert "break" statements, and it doesn't throw an error for missing "break" statements.