要实现从getList()下载JSON响应数据并以CSV或Excel格式保存，可以按照以下步骤进行：

1. 创建一个Angular服务来处理数据下载和转换的逻辑。可以使用HttpClient来发送GET请求并获取JSON响应数据。在这个服务中，还需要使用第三方库来将JSON转换为CSV或Excel格式。

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { saveAs } from 'file-saver';
import * as XLSX from 'xlsx';

@Injectable()
export class DownloadService {
  constructor(private http: HttpClient) {}

  getList() {
    return this.http.get('your-api-url');
  }

  downloadCSV(data: any[], filename: string) {
    const csvContent = this.convertToCSV(data);
    this.saveToFile(csvContent, 'text/csv', filename);
  }

  downloadExcel(data: any[], filename: string) {
    const excelContent = this.convertToExcel(data);
    this.saveToFile(excelContent, 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', filename);
  }

  private convertToCSV(data: any[]) {
    // Convert JSON to CSV format
    const csvRows = [];
    const headers = Object.keys(data[0]);
    csvRows.push(headers.join(','));

    for (const row of data) {
      const values = headers.map(header => {
        const escaped = (''+row[header]).replace(/"/g, '\\"');
        return `"${escaped}"`;
      });
      csvRows.push(values.join(','));
    }

    return csvRows.join('\n');
  }

  private convertToExcel(data: any[]) {
    // Convert JSON to Excel format using XLSX library
    const worksheet = XLSX.utils.json_to_sheet(data);
    const workbook = { Sheets: { 'data': worksheet }, SheetNames: ['data'] };
    const excelBuffer = XLSX.write(workbook, { bookType: 'xlsx', type: 'array' });
    return excelBuffer;
  }

  private saveToFile(content: any, type: string, filename: string) {
    const blob = new Blob([content], { type: type });
    saveAs(blob, filename);
  }
}

2. 在组件中使用该服务来获取数据并下载为CSV或Excel文件。

import { Component } from '@angular/core';
import { DownloadService } from './download.service';

@Component({
  selector: 'app-download',
  template: `
    Download as CSV
    Download as Excel
  `
})
export class DownloadComponent {
  constructor(private downloadService: DownloadService) {}

  downloadCSV() {
    this.downloadService.getList().subscribe(data => {
      this.downloadService.downloadCSV(data, 'data.csv');
    });
  }

  downloadExcel() {
    this.downloadService.getList().subscribe(data => {
      this.downloadService.downloadExcel(data, 'data.xlsx');
    });
  }
}

3. 在模块中声明和提供服务。

import { NgModule } from '@angular/core';
import { HttpClientModule } from '@angular/common/http';
import { DownloadService } from './download.service';
import { DownloadComponent } from './download.component';

@NgModule({
  imports: [HttpClientModule],
  declarations: [DownloadComponent],
  providers: [DownloadService],
  exports: [DownloadComponent]
})
export class DownloadModule { }

现在，当用户点击"Download as CSV"按钮时，会将getList()的响应数据下载为CSV文件。点击"Download as Excel"按钮时，会将响应数据下载为Excel文件。