fetch简单的分段上传

        methods: {
            async upfile() {
                let upload = document.getElementById("file1");
                let f = upload.files[0];
                let size = 1024 * 100;
                let start = 0,
                    end = 0;
                let data;
                while (start < f.size) {
                    end += size;
                    if (end > f.size) end = f.size;
                    console.log("size: %d start: %d end: %d ", f.size, start, end);
                    data = f.slice(start, end);
                    start = end;
                    let r = await fetch("http://127.0.0.1:8080/upload", {
                        method: "POST",
                        body: data,
                    });
                    console.log(await r.json());
                    data = null;
                }
            },