img中的blob链接怎么识别MIME类型?

function getFileMimeType(url) {
  return new Promise((resolve, reject) => {
    var xhr = new XMLHttpRequest()
    xhr.open("GET", url)
    xhr.responseType = "blob"
    // 加载时处理
    xhr.onload = () => {
     // 获取返回结果
      blob = xhr.response.type
      console.log(blob);
      resolve(blob)
    }
    xhr.onerror = (e) => {
      reject(e)
    }
    // 发送
    xhr.send()
  })
}
// 换成blob链接试试
let blobUrl = 'https://p9-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/d62d4705a29549488d443045de14a4fe~tplv-k3u1fbpfcp-zoom-crop-mark:3024:3024:3024:1702.awebp'
getFileMimeType(blobUrl)
 .then((response)=>{
    console.log(response)
 })
 .catch((e)=>{
    console.error(e)
 })