js如何获取图片url的Blob值并预览示例代码

//获取图片的Blob值
function getImageBlob(url, cb) {
 var xhr  = new XMLHttpRequest();
 xhr.open("get", url, true);
 xhr.responseType = "blob";
 xhr.onload = function() {
 if (this.status == 200) {
  if(cb) cb(this.response);
 }
 };
 xhr.send();
}

function preView(url){
 let reader = new FileReader();

 getImageBlob( url , function(blob){
 reader.readAsDataURL(blob);
 });

 reader.onload = function(e) {
 var img = document.createElement("img");
 img.src = e.target.result;
 document.body.appendChild(img);
 }
}