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");
  }
}