JavaScript Specialist Flashcards

Which JavaScript method returns a new array containing only elements that pass a provided test function?

Answer: filter()

filter() creates a new array with all elements for which the callback returns a truthy value.

What does the 'this' keyword refer to inside an arrow function?

Answer: The enclosing lexical context

Arrow functions do not have their own 'this'; they inherit it from the surrounding lexical scope.

Which event is fired when the browser has fully loaded the HTML and built the DOM, but before images and stylesheets finish loading?

Answer: DOMContentLoaded

DOMContentLoaded fires when the HTML document is fully parsed and the DOM is ready, without waiting for external resources.

What is the result of: typeof null in JavaScript?

Answer: 'object'

typeof null returns 'object' due to a historic bug in JavaScript that was never corrected for backward compatibility.

Which Array method executes a reducer function on each element and returns a single accumulated value?

Answer: reduce()

reduce() applies a callback function against an accumulator and each element to reduce the array to a single value.

In JavaScript, what does the spread operator (...) do when used with an array?

Answer: Expands the array into individual elements

The spread operator unpacks an array's elements so they can be passed individually as function arguments or combined into another array.

Which JavaScript statement is used to exit a loop immediately?

Answer: break

The break statement terminates the current loop or switch statement and transfers control to the code following it.