原生fetch获取下载速度

fetch-speed.js

let res = await fetch("https://api.wuuconix.link/setu?redirect")  // at this time, the header is ok
const bytesTotal = res.headers.get("content-length")
const reader = res.body.getReader()
let bytesRead = 0
const startTime = +Date.now()
while (true) {
  const { done, value } = await reader.read()
  if (value) {
    bytesRead += value.length
    const nowTime = +Date.now()
    const speed = (bytesRead / (nowTime - startTime)).toFixed(2)
    console.log(`已经读取 ${bytesRead}B / ${bytesTotal}B ${speed}KB/s`)
  }
  if (done) {
    break
  }
}

snapshot: