Convert image to base64 from URL

imageToBase64

static getDataUri (url) {
  return new Promise((resolve, reject) => {
    var image = new window.Image()
    image.crossOrigin = 'Anonymous'

    image.onload = function () {
      var canvas = document.createElement('canvas')
      window.alert('创建了 Canvas')
      window.alert(canvas)
      canvas.width = image.width
      canvas.height = image.height

      canvas.getContext('2d').drawImage(image, 0, 0)

      resolve(canvas.toDataURL())
    }

    image.src = url
  })
}
static toDataUrl (url) {
  return new Promise((resolve, reject) => {
    var xhr = new XMLHttpRequest()
    window.alert('xml method')
    xhr.onload = function () {
      window.alert('xml method 1')
      var reader = new FileReader()
      window.alert('xml method 2')
      reader.onloadend = function () {
        resolve(reader.result)
      }
      reader.readAsDataURL(xhr.response)
    }
    xhr.open('GET', url)
    xhr.responseType = 'blob'
    xhr.send()
    window.alert('xml method 2')
  })