vant/packages/vant-use/src/utils.ts

export const inBrowser = typeof window !== 'undefined';

const root = (inBrowser ? window : global) as Window;

let prev = Date.now();

function rafPolyfill(fn: FrameRequestCallback): number {
  const curr = Date.now();
  const ms = Math.max(0, 16 - (curr - prev));
  const id = setTimeout(fn, ms);
  prev = curr + ms;
  return id;
}

export function raf(fn: FrameRequestCallback): number {
  const requestAnimationFrame = root.requestAnimationFrame || rafPolyfill;
  return requestAnimationFrame.call(root, fn);
}

export function cancelRaf(id: number) {
  const cancelAnimationFrame = root.cancelAnimationFrame || root.clearTimeout;
  cancelAnimationFrame.call(root, id);
}

// double raf for animation
export function doubleRaf(fn: FrameRequestCallback): void {
  raf(() => {
    raf(fn);
  });
}