Prioritized Task Scheduling API https://medium.com/airbnb-engineering/building-a-faster-web-experience-with-the-posttask-scheduler-276b83454e91 https://web.dev/optimize-long-tasks/ 目的:方便取消、调整任务优先级 异步,安排在宏任务中 user-blocking 和 user-visible 类似,只是后者排在前者后面 background 类似 requestIdleCallback() ,最低优先级 scheduler.yield() 让任务连续执行,不被第三方代码插入任务