可以参考文章： https://juejin.im/post/5a14e9edf265da4312808d86
https://juejin.im/post/5a9108b6f265da4e7527b1a4#comment https://segmentfault.com/a/1190000016960203 https://segmentfault.com/a/1190000007409168 https://github.com/Kelichao/javascript.basics/issues/22
