feat(elements): implement registerAsCustomElements()

closes #19469

packages/elements/src/register-as-custom-elements.ts

@@ -0,0 +1,37 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {NgModuleFactory, NgModuleRef, PlatformRef, Type} from '@angular/core';
+
+import {NgElements} from './ng-elements';
+import {isFunction} from './utils';
+
+/**
+ * TODO(gkalpak): Add docs.
+ * @experimental
+ */
+export function registerAsCustomElements<T>(
+    customElementComponents: Type<any>[], platformRef: PlatformRef,
+    moduleFactory: NgModuleFactory<T>): Promise<NgModuleRef<T>>;
+export function registerAsCustomElements<T>(
+    customElementComponents: Type<any>[],
+    bootstrapFn: () => Promise<NgModuleRef<T>>): Promise<NgModuleRef<T>>;
+export function registerAsCustomElements<T>(
+    customElementComponents: Type<any>[],
+    platformRefOrBootstrapFn: PlatformRef | (() => Promise<NgModuleRef<T>>),
+    moduleFactory?: NgModuleFactory<T>): Promise<NgModuleRef<T>> {
+  const bootstrapFn = isFunction(platformRefOrBootstrapFn) ?
+      platformRefOrBootstrapFn :
+      () => platformRefOrBootstrapFn.bootstrapModuleFactory(moduleFactory !);
+
+  return bootstrapFn().then(moduleRef => {
+    const ngElements = new NgElements(moduleRef, customElementComponents);
+    ngElements.register();
+    return moduleRef;
+  });
+}