Adds some JS to every page as part of an SPFx Application Customizer.

COBSPFxApplicationCustomizer_GlobalJS.ts

export default class CobGlobalJsApplicationCustomizer
  extends BaseApplicationCustomizer<ICobGlobalJsApplicationCustomizerProperties> {

  private _externalJsUrl: string = "https://sharepointnutsandbolts.azurewebsites.net/scripts/SPFxGlobalScript.js";

  @override
  public onInit(): Promise<void> {
    console.log(`CobGlobalJsApplicationCustomizer.onInit(): Entered.`);
    
    let scriptTag: HTMLScriptElement = document.createElement("script");
    scriptTag.src = this._externalJsUrl;
    scriptTag.type = "text/javascript";
    document.getElementsByTagName("head")[0].appendChild(scriptTag);

    console.log(`CobGlobalJsApplicationCustomizer.onInit(): Added script link.`);
    console.log(`CobGlobalJsApplicationCustomizer.onInit(): Leaving.`);
    return Promise.resolve<void>();
  }
    
  // other methods omitted..
}