Javascript裡有如下的寫法，可以用在定義方法時，或者定義方法時用在方法的引數上，非常靈活

• 定義方法時

export class ExcelOperationA {
  constructor() {}
  public exportExcelA: () => void;
}

import { createXlsx } from './create-xlsx';
import { ExcelOperationA } from './ExcelOperationA';
@Component({
  selector: 'app-classNameB',
  templateUrl
 
: './ClassNameB.html'
})
export class ClassNameB {
  constructor(
    public excelOperationA: ExcelOperationA
  ) {
    this.excelOperationA.exportExcelA= () => createXlsx(parameterA);
  }
}

@Component({
  selector: 'rms-pt',
  templateUrl: `<app-classNameB [datas]="datas"></app-classNameB
 
>`
})
export class RmsPtComponent {
  public datas: Data[] = [];
  constructor(private public excelOperationA: ExcelOperationA) {}
  public excelDownloadHandle() {
    this.excelOperationA.exportToExcel();
  }
}