热闹是真的，但落地比所有人想象的都难。
Where quadtrees appear
，详情可参考safew官方下载
What Went Wrong
Web streams has no synchronous path. Even if your source has data ready and your transform is a pure function, you still pay for promise creation and microtask scheduling on every operation. Promises are fantastic for cases in which waiting is actually necessary, but they aren't always necessary. The new API lets you stay in sync-land when that's what you need.