js上传文件file转ArrayBuffer

var file = this.fileUploaded[0];

var fr = new FileReader();
var filename = file.name;
fr.readAsArrayBuffer(file);
fr.addEventListener("loadend", (e) => {
var buf = e.target.result;//读取完毕后的buffer数组
// cb(buf, filename);
new Promise((resolve, reject) => {
const result = client.put('exampleobject.txt', buf);
resolve(result); //完成后调用 resolve，就会跑到then里面，可以有参数，会传到then里面
}).then((result) => {
//自己编写后续逻辑
console.log(result);
});
}, false);