AI solution for Interview Question on BFE.dev
42. What is the difference between Repaint and Reflow?

Repaint and Reflow are two terms used in web development to describe different processes that occur when rendering a webpage in a browser.

Reflow: Reflow happens when the browser updates the layout of the page. It occurs when changes are made to the DOM (such as adding or removing elements or changing styles). The browser reads these changes and figures out the current state of the page, then recalculates its layout and re-renders it on the screen. Reflow is a computationally intensive process that can slow down the rendering process of a web page.

Repaint: Repaint happens when the browser updates the visual appearance of an element on the page, without changing its layout. It may occur when changes in colors, backgrounds, borders, or font styles are made. The browser reads the changes, repaints the affected elements, and redraws them on the screen.

In summary, repaint involves changes to the visual appearance of an already-rendered element, while reflow involves changes to the layout of the entire page. Reducing the number or frequency of reflows and repaints can significantly improve the performance of a web page.