js将后台的blob格式图片显示在本地

直接上代码：
var xhr = new XMLHttpRequest();
xhr.responseType = “blob”;
xhr.open(“GET”,url,true);
xhr.setRequestHeader(key,value);
xhr.onload = function(){
if(xhr.status == 200){
var blob = this.response;
var img = new Image();
img.width = 200;
img.height = 200;
img.onload = function(){
window.URL.revokeObjectURL(img.src);
}
img.src = window.URL.createObjectURL(blob);
}
}
xhr.send();