21.上传下载excle文件

 var wb;//读取完成的数据
            var rABS = false; //是否将文件读取为二进制字符串


            function fixdata(data) { //文件流转BinaryString
                var o = "",
                    l = 0,
                    w = 10240;
                for (; l < data.byteLength / w; ++l) o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w, l * w + w)));
                o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w)));
                return o;
            }


            $("#file").change(function () {
                if (!this.files) {
                    return;
                }
                var f = this.files[0];
                var reader = new FileReader();
                reader.onload = function (e) {
                    var data = e.target.result;
                    if (rABS) {
                        wb = XLSX.read(btoa(fixdata(data)), {
                            type: 'base64'
                        });
                    } else {
                        wb = XLSX.read(data, {
                            type: 'binary'
                        });
                    }
                    console.log(wb)
                    // document.getElementById("demo").innerHTML = JSON.stringify(XLSX.utils.sheet_to_json(wb.Sheets[wb.SheetNames[0]]));
                };
                if (rABS) {
                    reader.readAsArrayBuffer(f);
                } else {
                    reader.readAsBinaryString(f);
                }
            })

            // 导出excle数据
            $('#btn').on('click', function() {
                var ws = XLSX.utils.json_to_sheet(users);/* 新建空workbook，然后加入worksheet */
                var wb = XLSX.utils.book_new();/*新建book*/
                XLSX.utils.book_append_sheet(wb, ws, "People");/* 生成xlsx文件(book,sheet数据,sheet命名) */
                XLSX.writeFile(wb, "sheetjs.xlsx");
            })