typescript - Angular 和 firebase [push 不是一個函數]

我在使用 Angular 和 Firebase 時遇到錯誤：

錯誤 TypeError: _this.accounts.push 不是一個函數 在 auth.service.ts:25 在 e.g (auth.esm.js:17) 在 Fb (auth.esm.js:20) 在 Bb (auth.esm.js:20) 在 A.push../node_modules/@firebase/auth/dist/auth.esm.js.g.Xb (auth.esm.js:19) 在 kb (auth.esm.js:13) 在 ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:388) 在 Object.onInvoke (core.js:3824) 在 ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:387) 在 Zone.push../node_modules/zone.js/dist/zone.js.Zone.run (zone.js:138)

auth.service.ts ：

import { Injectable } from '@angular/core';
import { Subject } from 'rxjs';
import { Account } from '../models/Account.model'
import * as firebase from 'firebase';
import DataSnapshot = firebase.database.DataSnapshot;

@Injectable({
    providedIn: 'root'
})
export class AuthService {

    accounts: Account[] = [];
    accountsSubject = new Subject<Account[]>;

    constructor() {
        this.getAccounts();
    }

    createNewUser(email: string, password: string, newAccount: Account) {
        return new Promise(
            (resolve, reject) => {
                firebase.auth().createUserWithEmailAndPassword(email, password).then(
                    () => {
                        resolve();
                        this.accounts.push(newAccount); // <-- 25
                        this.saveAccounts();
                        this.emitAccounts();
                    },
                    (error) => {
                        reject(error);
                    }
                    );
            }
            );
    }
    emitAccounts(){
        this.accountsSubject.next(this.accounts);
    }
    saveAccounts(){
        firebase.database().ref('/accounts').set(this.accounts);
    }
    getAccounts(){  
        firebase.database().ref('/accounts')
        .on('value', (data: DataSnapshot) => {
            this.accounts = data.val() ? data.val() : [];
            this.emitAccounts();
        }
        );
    }
    signInUser(email: string, password: string) {
        return new Promise(
            (resolve, reject) => {
                firebase.auth().signInWithEmailAndPassword(email, password).then(
                    () => {
                        resolve();
                    },
                    (error) => {
                        reject(error);
                    }
                    );
            }
            );
    }

    signOutUser() {
        firebase.auth().signOut();
    }

}

提前致謝。傑瑞米