NativeScript/nativescript-core/globals/index.ts

export let hasInitGlobal = false;

function registerOnGlobalContext(moduleName: string, exportName: string): void {
  Object.defineProperty(global, exportName, {
    get: function () {
      // We do not need to cache require() call since it is already cached in the runtime.
      let m = global.loadModule(moduleName);

      // Redefine the property to make sure the above code is executed only once.
      let resolvedValue = m[exportName];
      Object.defineProperty(global, exportName, {
        value: resolvedValue,
        configurable: true,
        writable: true,
      });

      return resolvedValue;
    },
    configurable: true,
  });
}

export function installPolyfills(moduleName: string, exportNames: string[]) {
  if (global.__snapshot) {
    const loadedModule = global.loadModule(moduleName);
    exportNames.forEach((exportName) => (global[exportName] = loadedModule[exportName]));
  } else {
    exportNames.forEach((exportName) => registerOnGlobalContext(moduleName, exportName));
  }
}

export function initGlobal() {
  console.log('initPolyfills called, init:', hasInitGlobal);
  if (!hasInitGlobal) {
    hasInitGlobal = true;
    // apply global polyfills first
    require('./core');

    // DOM api polyfills
    global.registerModule('timer', () => require('../timer'));
    installPolyfills('timer', ['setTimeout', 'clearTimeout', 'setInterval', 'clearInterval']);

    global.registerModule('animation', () => require('../animation-frame'));
    installPolyfills('animation', ['requestAnimationFrame', 'cancelAnimationFrame']);

    global.registerModule('ui-dialogs', () => require('../ui/dialogs'));
    installPolyfills('ui-dialogs', ['alert', 'confirm', 'prompt', 'login', 'action']);

    global.registerModule('text', () => require('../text'));
    installPolyfills('text', ['TextDecoder', 'TextEncoder']);

    global.registerModule('xhr', () => require('../xhr'));
    installPolyfills('xhr', ['XMLHttpRequest', 'FormData', 'Blob', 'File', 'FileReader']);

    global.registerModule('fetch', () => require('../fetch'));
    installPolyfills('fetch', ['fetch', 'Headers', 'Request', 'Response']);

    // Custom decorators
    require('./decorators');
  }
}