function imgLoad(url) {
    // 用兩個參數, resolve和reject
    return new Promise(function(resolve, reject) {
      var request = new XMLHttpRequest();
      request.open('GET', url)
      request.responseType = 'blob'

      // onload
      request.onload = function() {
        if (request.status === 200) {
           // 成功響應
          resolve(request.response);
        } else {
          reject(Error(request.statusText));
        }
      }

      // onerror
      request.onerror = function() {
          reject(Error('加載失敗'))
      };
      // 發送請求
      request.send()
    })
  }

  var body = document.querySelector('body');
  var myImage = new Image();
  imgLoad('blob:https://mdn.github.io/f84ebba6-8b10-4165-8704-47923e6129e1')
    .then(function(response) {
        var imageURL = window.URL.createObjectURL(response)
        myImage.src = imageURL
        body.appendChild(myImage)
    },
    function(Error) {
        console.log(Error)
    })

參考：

https://mdn.github.io/js-examples/promises-test/