var path= require(“path”)；
path.extname();
fs.ReadStream
fs.exists(path, callback) 已废弃
fs.createReadStream.pipe()
读取视频 https://blog.csdn.net/liuyaqi1993/article/details/76560401
https://blog.csdn.net/xiaopeng_han123/article/details/78595063
原文：https://www.cnblogs.com/zzxuan/p/9286790.html