关于javascript：(Angular2)无法读取toastr的undefined属性’extend’

(Angular2) Cannot read property 'extend' of undefined for toastr

我正在尝试将angularjs 2中的toastr用作一项服务，如下所述将其注入到我的组件中。调用handleEvent函数时，我收到"无法读取未定义的属性\\'extend \\'"。对该错误的任何建议和/或解释，我们深表感谢。

app.moudle.ts已导入ToastrService，并且ToastrService已添加到提供程序中。

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//events/events-list.components.ts

import { ToastrService } from '../common/toastr.service';
@Component ({
selector: 'event-list',
template: `

Upcoming Angular 2 Event

<event-thumbnail (click)="handleEvent(event_data.name)" [event]="event_data"></event-thumbnail>

`
})

export class EventListComponent implements OnInit {
all_data:any[]
constructor(private eventService : EventService , private toastr : ToastrService ){
//moved code from here to ngOnInit
}

ngOnInit(){
this.all_data = this.eventService.getEvents();
}

handleEvent(eventName) {
console.log("hey here "+eventName);
this.toastr.success(eventName);
}
}

错误：
[在console.log输出之后抛出此错误]

EXCEPTION: Error in ./EventListComponent class EventListComponent -
inline template:6:16 caused by: Cannot read property 'extend' of
undefined.
ORIGINAL EXCEPTION: Cannot read property 'extend' of undefined
TypeError: Cannot read property 'extend' of undefined
at m (toastr.js:411)
at Object.s [as success] (toastr.js:85)
at ToastrService.success (toastr.service.ts:12)