instanceof@tg says to YSITD 好，那我修正一下 JS 本身不 multithread 但 V8 讓它在某些地方可以以 multithread 執行 https://www.quora.com/Why-is-Node-js-single-threaded-Is-it-a-constraint-of-the-V8-engine-or-of-the-JavaScript-language-itself