Front-End Development Flashcards

Which CSS property creates a new stacking context for an element?

Answer: position: relative with z-index

Setting position to relative, absolute, fixed, or sticky combined with a z-index value other than auto creates a new stacking context.

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

Answer: Expands the array into individual elements

The spread operator expands an iterable like an array into individual elements, useful for copying or merging arrays.

What is the purpose of the CSS `will-change` property?

Answer: Hints to the browser which properties will animate for optimization

The `will-change` property informs the browser ahead of time which properties will change, allowing it to set up optimizations like compositing layers.

Which HTTP status code indicates a resource has been permanently moved?

Answer: 301

301 Moved Permanently tells the client and search engines that the resource has permanently moved to a new URL.

In React, when does `useEffect` with an empty dependency array run?

Answer: Only once after the initial render

An empty dependency array `[]` causes useEffect to run only once after the component's initial mount, similar to componentDidMount.

What does the CSS `clip-path` property do?

Answer: Defines a visible region by clipping the element to a shape

The `clip-path` property clips an element to a defined shape such as a circle, polygon, or SVG path, hiding the parts outside the shape.

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

Answer: filter()

Array.prototype.filter() creates a new array containing only the elements for which the callback function returns true.