text: (function () {
      const express = require('express')
  
      const fs = require('fs')
  
      const app = express()
  
      app.get('/video', function (req, res) {
          let pathSrc = req.query.video
          let stat = fs.statSync(pathSrc);
          let fileSize = stat.size;
          let range = req.headers.range;
          // fileSize 3332038
          if (range) {
              //有range头才使用206状态码
              let parts = range.replace(/bytes=/, "").split("-");
              let start = parseInt(parts[0], 10);
              let end = parts[1] ? parseInt(parts[1], 10) : start + 999999;
      
              // end 在最后取值为 fileSize - 1 
              end = end > fileSize - 1 ? fileSize - 1 : end;
      
              let chunksize = (end - start) + 1;
              let file = fs.createReadStream(pathSrc, {
                  start,
                  end
              });
              let head = {
                  'Content-Range': `bytes ${start}-${end}/${fileSize}`,
                  'Accept-Ranges': 'bytes',
                  'Content-Length': chunksize,
                  'Content-Type': 'video/mp4',
              };
              res.writeHead(206, head);
              file.pipe(res);
          } else {
              let head = {
                  'Content-Length': fileSize,
                  'Content-Type': 'video/mp4',
              };
              res.writeHead(200, head);
              fs.createReadStream(pathSrc).pipe(res);
          }
      })
  
      app.listen(6789, () => {
          console.log('localhost:6789')
      })
  
  })()