Angular 2 - Execute code when closing window

Thanks everyone for the help. I was able to create a solution based on different proposal.

First I used the beforeunload event in the component

@HostListener('window:beforeunload', ['$event'])
beforeunloadHandler(event) {
    this.endChat();
}

where

endChat() {
    this.chatService.endChatSync(this.chatSessionInfo);
}

Then, the trick is to make the http call sync not async.

Before, the endchat method at the chat service was

    endChat(chatSessionInfo: ChatSessionInfo)  : Observable<ChatTranscription> {
    console.log("Ending chat..");
    let body = JSON.stringify(chatSessionInfo);
    let headers = new Headers({ 'Content-Type': 'application/json' });
    let options = new RequestOptions({ headers: headers });
    return this.http.delete(this.apiUrl + "Chat?userId="+chatSessionInfo.UserId+"&secureKey="+chatSessionInfo.SecureKey,options)
             .map(this.extractData)
            .catch(this.handleError);
}

I was able to make it work with

endChatSync(chatSessionInfo: ChatSessionInfo)  {
    console.log("Ending chat..");
     let xhr = new XMLHttpRequest()
     xhr.open("DELETE",this.apiUrl +"Chat?userId="+chatSessionInfo.UserId+"&secureKey="+chatSessionInfo.SecureKey,false);
     xhr.send();
}

Hope this helps!

@HostListener('window:unload', ['$event'])
unloadHandler(event) {
  ...
}

See also javascript to check when the browser window is close