need some help, for the life of me I can't get this to work. I'm trying to loop through an array which is within a config value and then trigger another function within the service I created, but I get an error

```
TypeError: Cannot read property 'registerToken' of undefined

```

Is there not a better way to do this it feels very clunky?

CampaignService.ts

```
import { ServerConfig } from "../core/ServerConfig";

declare var config: ServerConfig;

export class CampaignService {
  static $inject = ["localStorageService"];

  constructor(
    public localStorageService: angular.local.storage.ILocalStorageService
  ) {

  }             

  launchCampaign(campaignToken: string) {
    if (campaignToken) {
      config.campaigns.forEach(function (data) {
        if (campaignToken == data.title) {
          if (data.enabled) {
            this.registerToken(campaignToken);
          }
        }
      });
    }
  };

  registerToken(campaignToken: string) {

  }    

}

```