upyun 怎么用nodejs上传网络图片到upyun空间

Question

var UPYUN = require('upyun');
var upyun = new UPYUN(conf.upyun.bucket, conf.upyun.operator, conf.upyun.password, conf.upyun.endpoint, conf.upyun.apiVersion);

console.log(conf.upyun);
console.log(upyun);
upyun.getUsage(function(err, result) {
console.log(result);
});

 最后打印的result怎么是undifined？？？
 第一个和第二个log都是正常的
 用的官方的nodejs库node-upyun

 upyun 怎么用nodejs上传网络图片到upyun空间并返回相应的地址？