Angular：从FileReader返回Observable / ES6 Promise

发布时间：2020-12-17 06:49:42 所属栏目：安全来源：网络整理

导读：我试图从FileReader返回结果,我发现 this实现.但由于它已经过时,我想知道如何使用ES6 Promises或Rx Observable实现相同的功能. 下面是我的代码,参考上述链接,它按预期工作. import { Injectable } from '@angular/core';import * as XLSX from 'xlsx';import

我试图从FileReader返回结果,我发现 this实现.但由于它已经过时,我想知道如何使用ES6 Promises或Rx Observable实现相同的功能.

下面是我的代码,参考上述链接,它按预期工作.

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,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();
  }

}

在消费者组件中

this.excelReaderService.importFromExcel(ev).then((result) => {
    this.detailHeadings = Object.keys(result[0]);
    this.detailData = result;
})

如果有人帮助我,因为我是异步编程的新手,这将是很棒的.

解决方法

这就是我做的方式,如果有人想要一个Angular服务,它读取Excel文件并以可观察的内容作为JSON进行响应.

我正在使用SheetJS来读取文件并输出JSON.

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import * as XLSX from 'xlsx';

@Injectable()
export class ExcelReaderService {

  constructor() { }

  importFromExcel(ev): Observable<any> {
    let workbook;
    let excelInJSON;

    const fileReader = new FileReader();

    // init read
    fileReader.readAsArrayBuffer((<any>ev.target).files[0]);

    return Observable.create(observer => {
      // if success
      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
        workbook = XLSX.read(binary,cellStyles: true });
        // only first sheet
        excelInJSON = XLSX.utils.sheet_to_json(workbook.Sheets[workbook.SheetNames[0]]);

        observer.next(excelInJSON);
      }

      // if failed
      fileReader.onerror = error => observer.error(error);
    });
  }

}

从组件中,只需将事件传递给此服务,如下所示,它将使用JSON进行响应.

this.excelReaderService.importFromExcel(ev)
  .subscribe(response => {
    // do something with the response
  });

（编辑：李大同）

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