Glossary coding Term Page
Layout Thrashing
Rapidly mixing layout reads and writes that trigger needless recalculations.
Core Idea
Layout thrashing happens when scripts ask for layout metrics—like offsetHeight—right after mutating the DOM, forcing the browser to recalc immediately. Repeating that pattern per item multiplies reflow cost and tanks frame rates.
Why It Matters Here
Mathbong demonstrates thrashing so readers see how batching via DocumentFragment or scheduling via requestAnimationFrame removes the sawtooth pattern. Keeping this term explicit helps teams audit render helpers before they grow into performance hotspots.