SOURCE

function imgLoad (url) {
  return new Promise ( (resolve, reject) => {
    const xhr = new XMLHttpRequest()
    xhr.open('GET', url)
    xhr.responseType = 'blob'
    console.log('使用 XHR 加载图像', xhr.status)
    
    xhr.onload = () => {
     
      if(xhr.status === 200) {
        resolve(xhr.response)
      } else {
        reject (Error('Image do not load successfully, error code:' + xhr.statusText) )
      }
    }
    xhr.onerror = () => {
      reject(Error('There was a network error'))
    }
    xhr.send()
  })
}

let body = document.querySelector('body')
let myImage = new Image()
// imgLoad('XXX.jpg').then( (response) => {
imgLoad('https://mdn.mozillademos.org/files/8633/promises.png').then( (response) => {
  let imageUrl = window.URL.createObjectURL(response)
  myImage.src = imageUrl
  body.addendChild(imageUrl)
}, (Error) => {
  console.log('then--error', Error)
})