I was trying to return result from FileReader
and I found this implementation. But since it is outdated, I'm wondering how to implement the same using ES6 Promises
or Rx Observables
.
Below is my code with reference to the aforementioned link and it works as expected.
import { Injectable } from '@angular/core';
import * as XLSX from 'xlsx';
import * as XLS from 'xlsx';
@Injectable()
export class ExcelReaderService {
constructor() { }
importFromExcel(ev): JQueryPromise<any> {
let deferred = $.Deferred();
let regex = /^([a-zA-Z0-9s_\.-:])+(.xlsx|.xls)$/;
let workbook;
let excelInJSON;
if (regex.test(ev.target.files[0].name.toString().toLowerCase())) {
let xlsxflag = false; /*Flag for checking whether excel is .xls format or .xlsx format*/
if (ev.target.files[0].name.toString().toLowerCase().indexOf(".xlsx") > 0) {
xlsxflag = true;
}
let fileReader = new FileReader();
fileReader.onload = (ev) => {
let binary = "";
let bytes = new Uint8Array((<any>ev.target).result);
let length = bytes.byteLength;
for (let i = 0; i < length; i++) {
binary += String.fromCharCode(bytes[i]);
}
/*Converts the excel data in to json*/
if (xlsxflag) {
workbook = XLSX.read(binary, { type: 'binary', cellDates: true, cellStyles: true });
// only first sheet
excelInJSON = XLSX.utils.sheet_to_json(workbook.Sheets[workbook.SheetNames[0]]);
deferred.resolve(excelInJSON);
}
else {
workbook = XLS.read(binary, { type: 'binary', cellDates: true, cellStyles: true });
excelInJSON = <{}[]>XLS.utils.sheet_to_row_object_array(workbook.Sheets[workbook.SheetNames[0]]);
deferred.resolve(excelInJSON);
}
}
// init read
if (xlsxflag)
fileReader.readAsArrayBuffer((<any>ev.target).files[0]);
else
fileReader.readAsBinaryString((<any>ev.target).files[0]);
} else {
deferred.reject('Invalid file!');
}
return deferred.promise();
}
}
In the consumer component
this.excelReaderService.importFromExcel(ev).then((result) => {
this.detailHeadings = Object.keys(result[0]);
this.detailData = result;
})
It'll be great if someone helps me with this as I'm new to asynchronous programming.
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