检查打字稿中是否存在函数

Question

我正在将js代码转换为typescript（angular 1到2）......痛苦的操作！

if (_usersDatabase.updateReplication == null) {下方的行会导致打字稿错误：

Typescript Error
Property 'updateReplication' does not exist on type 'Database<{}>'.

。它是为了检查函数是否已经定义。

我怎么能为打字稿写这个？

import { MigrationService } from '../providers/migration-service';
import { CouchConstants } from '../couch-constants';
import * as PouchDB from 'pouchdb';

@Injectable()
export class UsersDatabase {

    constructor(
        private storageService: LocalStorageService
        , private UtilsService: UtilsService
        , private MigrationService: MigrationService

    ) {

    'use strict';

    var _usersDatabase = new PouchDB(CouchConstants.COUCHDB_USERS_DB_NAME);

    if (_usersDatabase.updateReplication == null) {

        _usersDatabase.updateReplication = function (newDocsIds) {

Answer 1

• 无需在打字稿文件
中使用'use strict';

• 使用this访问他们的方法和变量。

  @Injectable()
  export class UsersDatabase {
  private _usersDatabase : any;
  
  constructor(
      private storageService: LocalStorageService
      , private UtilsService: UtilsService
      , private MigrationService: MigrationService
  
  ) {
  
  this._usersDatabase = new PouchDB(CouchConstants.COUCHDB_USERS_DB_NAME);
  
  if (this._usersDatabase.updateReplication == null) {
  
          this._usersDatabase.updateReplication = function (newDocsIds) {
  
          }
   }
  }