Many developers assume setTimeout(fn, 0) runs instantly.It never does. Why JavaScript has a single-threaded event loop setTimeout callbacks go to the macrotask queue Rendering, promises, microtasks run first console.log(‘A’); setTimeout(() => console.log(‘B’), 0); Promise.resolve().then(() => console.log(‘C’)); console.log(‘D’); Output A D C B Impact Race conditions UI glitches Unexpected async order Fix Use microtasks when order […]