In which scenario might you prefer to use Object.create(null) over {} to create an empty object?

When you need an empty object with no prototype chain (no inherited properties or methods)
When you need an empty object with default prototype properties
When you need an object with prototype properties
When you need an object with getter and setter methods

Object.create(null) is used when you want an empty object with no prototype chain. This is useful when you want to create a clean slate object without inheriting any properties or methods from the Object prototype.

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The insertBefore method is used to insert an element before the _________ child of a specified parent.

first
last
next
previous

The insertBefore method is used to insert an element before the specified next child of a parent element. It allows you to precisely control the position of the new element within the parent's children.

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How do you select the last child of an element using pure JavaScript?

lastChild
element.lastChild
lastElementChild
element.lastElementChild

To select the last child of an element using pure JavaScript, you should use the lastElementChild property of the element. This property returns the last element among the child elements of the specified parent element. The other options, lastChild, element.lastChild, and lastElementChild, do not provide the same functionality.

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You are reading through a codebase and find that a block of code within an "else if" statement is not being executed, despite it seeming like the condition should be true. What are some steps you could take to troubleshoot this issue?

Check condition logic
Verify variable values
Examine code dependencies
Debug with console statements

Troubleshooting such issues involves checking the condition logic within the "else if" statement. Verify that the condition is correctly formulated and that the variables being compared have the expected values. Additionally, inspecting code dependencies and using console statements for debugging can help identify the problem.

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You’re developing a web application and need to add a feature where a modal appears when a button is clicked, but users complain that the page scrolls up every time they click the button. What JavaScript method could you use to prevent this default behavior?

event.stopPropagation()
event.preventDefault()
event.stopImmediatePropagation()
event.cancelBubble()

To prevent the default behavior of a button click, you can use the event.preventDefault() method. This method stops the browser from executing the default action associated with the event, such as submitting a form or navigating to a new page, in this case, preventing the page from scrolling up. event.stopPropagation() is used to stop the event from bubbling up the DOM tree but won't prevent the default behavior.

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During a project review, a colleague points out that a piece of code might have a performance impact due to creating a new scope each time it runs. Which type of function is being used: a regular function or an arrow function?

Regular function
Arrow function
Both regular and arrow functions
It depends on the JavaScript engine used

The piece of code that creates a new scope each time it runs is likely using an arrow function. Arrow functions capture the scope they are created in, which can lead to performance implications when they are used within loops or frequently called functions. Regular functions, on the other hand, do not capture the scope and may be more suitable for certain performance-critical scenarios.

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Which looping statement is suitable when the number of iterations is not known beforehand?

for loop
while loop
do...while loop
forEach loop

A while loop is suitable when the number of iterations is not known beforehand. It allows you to repeat a block of code as long as a specified condition is true. This makes it a flexible choice for situations where the loop's exit condition isn't predetermined.

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In what scenario might a do-while loop be preferred over a while loop, considering best practices?

When you want to ensure the loop body runs at least once, regardless of the condition.
When you need to perform a specific number of iterations.
When you want to optimize loop performance for shorter conditions.
When you want to break out of the loop early based on a condition.

A do-while loop is preferred when you want to ensure that the loop body runs at least once, regardless of the condition. This is useful in scenarios where you need to perform an action before evaluating the loop condition.

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In JavaScript, the ________ object represents the eventual

EventEmitter
Promise
Callback
Observable

In JavaScript, the Promise object represents the eventual completion or failure of an asynchronous operation. Promises are widely used for handling asynchronous tasks, providing a cleaner and more structured way to work with asynchronous code.

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Which method is used to select an element by its ID in JavaScript?

getElementByTag
getElementById
getElementByClass
querySelector

The correct method to select an element by its ID in JavaScript is getElementById. This method retrieves an element by its unique ID attribute. The other options do not select elements by their IDs.

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