angular2异步执行

Question

我在 ts 文件中有多个功能，如下所示。

reply_click(event) {
        var target = event.target || event.srcElement || event.currentTarget;
        var idAttr = target.attributes.id;
        sessionStorage.setItem('geo', idAttr.nodeValue);
        var value = sessionStorage.getItem('geo');
        var NT = sessionStorage.getItem('NTsession');
        var sesssion = sessionStorage.getItem('EmployeeDetail');
        var ses = JSON.parse(sesssion);
        var intEmPKNo = ses[0].EmPKNo;
        var GeoList = ses[0].GeoList.substring(0, 3);
        if (GeoList != value)
            this.router.navigateByUrl('/notAuthorized');
        else {
            this._userService.get(Global.BASE_USER_ENDPOINT + '/EmployeeInfo?intEmPKNo=' + intEmPKNo)
                .do(data => sessionStorage.setItem('EmployeeInfo', JSON.stringify(data)))
                .subscribe(dashboard => {
                    this.dashboard = dashboard; this.indLoading = false;
                    this.attendance();
                },
                error => this.msg = <any>error);
        }
    }
    attendance() {
        var NT = sessionStorage.getItem('NTsession');
        var sesssion = sessionStorage.getItem('EmployeeDetail');
        var ses = JSON.parse(sesssion);
        var intEmPKNo = ses[0].EmPKNo;
        this._userService.get(Global.BASE_USER_ENDPOINT + '/MyAttendance?intEmPKNo=' + intEmPKNo)
            .do(data => sessionStorage.setItem('MyAttendance', JSON.stringify(data)))
            .subscribe(dashboard => {
                this.dashboard = dashboard; this.indLoading = false;
                this.PayPollHealth();
            },
            error => this.msg = <any>error);
    }
    PayPollHealth() {
        var sesssion = sessionStorage.getItem('EmployeeDetail');
        var ses = JSON.parse(sesssion);
        var intEmPKNo = ses[0].EmPKNo;
        this._userService.get(Global.BASE_USER_ENDPOINT + '/PayrollHealth?intEmPKNo=' + intEmPKNo)
            .do(data => sessionStorage.setItem('PayRollHealth', JSON.stringify(data)))
            .subscribe(dashboard => {
            this.dashboard = dashboard; this.indLoading = false;
            this.router.navigateByUrl('/dashboard');
            },
            error => this.msg = <any>error);
    }

以便在执行所有函数后加载html，因为它需要将近30秒。

如何异步调用此函数？