无法在打字稿中访问全局变量

Question

我在代码中遇到了一个奇怪的问题。我在 class 中声明了 markers 变量，所以它是全局的，可以在 class 中的任何地方访问。但问题是我可以访问 initMap 内部的标记，但无法在 InitMap 的函数内部访问它。错误提示：TS2339 属性 'markers' 在类型 void

上不存在

 export class StudentGraphicReportMapComponent implements OnInit  {
  locations: any[] = [];
  markers:any[] = [];
  constructor(private http: Http, private  elementRef: ElementRef , private dashboardService: DashboardService) {
  }
  initMap() { 
   // ------ CAN ACCESS markers here
 
    this.locations.forEach(function(location: Location) {
         for ( let b = 0; b < location.studentCount; b++) {
           let marker = new google.maps.Marker({
             position: location,
             label: 'A'
           });
    // ----------CANNOT ACCESS markers here
           this.markers.push(marker); //Error:Property 'markers' does not exist on type void
         }
    });
  
  }
  ngOnInit() {
    this.dashboardService.getStudentCoordinates().then(data => {
      this.locations = data.data;
      this.initMap();
    });
  }

}

请帮我解决这个问题。亲切的问候

Answer 1

您应该像这样使用 arrow functions 访问 this：

export class StudentGraphicReportMapComponent implements OnInit  {
  locations: any[] = [];
  markers:any[] = [];
  constructor(private http: Http, private  elementRef: ElementRef , private dashboardService: DashboardService) {
  }
  initMap() { 
    this.locations.forEach((location: Location) => {
         for ( let b = 0; b < location.studentCount; b++) {
           let marker = new google.maps.Marker({
             position: location,
             label: 'A'
           });
           this.markers.push(marker); //Error:Property 'markers' does not exist on type void
         }
    });

  }
  ngOnInit() {
    this.dashboardService.getStudentCoordinates().then(data => {
      this.locations = data.data;
      this.initMap();
    });
  }

}

Answer 2

让局部变量指向这个

initMap() { 
let _self = this;
...
}

并在函数

中使用_self.markers

无法在打字稿中访问全局变量

Cannot access global variable in typescript

javascript

typescript

ecmascript-6

typescript2.0

angular