setTimeout(), setInterval(), and requestAnimationFrame()

let start = performance.now();
while (performance.now() - start < 1000) {
  // Busy loop
}
setTimeout(() => console.log('Timeout'), 0);

The while loop is incorrect
performance.now() is inaccurate
Synchronous code blocks the event loop
The timeout executes late because: 1) Synchronous loop blocks the event loop, 2) Timer callbacks can't execute until call stack is empty, 3) JavaScript is single-threaded, 4) Event loop is blocked during while execution, 5) Demonstrates importance of non-blocking code, 6) Common cause of performance issues.
setTimeout is broken