- first code with simple leaflet map

src/environments/environment.prod.ts

@@ -0,0 +1,3 @@
+export const environment = {
+  production: true
+};

src/environments/environment.ts

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+// This file can be replaced during build by using the `fileReplacements` array.
+// `ng build` replaces `environment.ts` with `environment.prod.ts`.
+// The list of file replacements can be found in `angular.json`.
+
+export const environment = {
+  production: false
+};
+
+/*
+ * For easier debugging in development mode, you can import the following file
+ * to ignore zone related error stack frames such as `zone.run`, `zoneDelegate.invokeTask`.
+ *
+ * This import should be commented out in production mode because it will have a negative impact
+ * on performance if an error is thrown.
+ */
+// import 'zone.js/plugins/zone-error';  // Included with Angular CLI.