js base64 七牛图片上传自定义路径

七牛云上传base64图片代码如下：

function dmaku(){
 var curTime = new Date().getTime()
 var str = 'sc/' + schoolid+'/' + taskid + '/'+curTime+'.png';
 str = btoa(str) //创建一个base64格式的字符串
 var pic = imgArr[index].replace(/^data:image\/\w+;base64,/, "")
  var pic = "填写你的base64后的字符串";
  var url = "http://upload.qiniup.com/putb64/-1/key/"+str; //非华东空间需要根据注意事项 1 修改上传域名
  var xhr = new XMLHttpRequest();
  xhr.onreadystatechange=function(){
    if (xhr.readyState==4){
      document.getElementById("myDiv").innerHTML=xhr.responseText;
    }
  }
  xhr.open("POST", url, true);
  xhr.setRequestHeader("Content-Type", "application/octet-stream");
  xhr.setRequestHeader("Authorization", "UpToken 填写你从服务端获取的上传token");
  xhr.send(pic);
}