refactor(router): create pipeable recognize function (#25740)

PR Close #25740

packages/router/src/operators/recognize.ts

@@ -0,0 +1,28 @@
+/**
+ * @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 {Type} from '@angular/core';
+import {Observable, OperatorFunction} from 'rxjs';
+import {mergeMap} from 'rxjs/operators';
+
+import {Route} from '../config';
+import {recognize as recognizeFn} from '../recognize';
+import {RouterStateSnapshot} from '../router_state';
+import {UrlTree} from '../url_tree';
+
+export function recognize(
+    rootComponentType: Type<any>| null, config: Route[], serializer: (url: UrlTree) => string,
+    paramsInheritanceStrategy: 'emptyOnly' |
+        'always'): OperatorFunction<UrlTree, RouterStateSnapshot> {
+  return function(source: Observable<UrlTree>) {
+    return source.pipe(mergeMap(
+        (appliedUrl: UrlTree) => recognizeFn(
+            rootComponentType, config, appliedUrl, serializer(appliedUrl),
+            paramsInheritanceStrategy)));
+  };
+}