how to embed an angular app into another app?
My team develop an angular 5 application that has been in production for a while, but we've been tasked recently with making the app work in other 3 sites the company owns. One site is a SPA built with Angular6, other is also a SPA but uses Angular5, while the other is using some older libraries such as jQuery.
Management wanted us to integrate with the Angular5 SPA right away so we just exported the whole application as a module with child routes and let the other application do the bootstrap.
But I'm afraid the above approach will not work for the non-angular site. This also tight couple both applications since the 'host' app needs to know about all dependencies of our application which is not a trivial app (I'd say is pretty big) and install them, this caused problems when both applications needed different versions of the same dependency, no to mention that we will need to sync when upgrading dependencies or the framework itself. I don't think this approach will scale when embedding the app into more sites.
My first idea for a more general implementation was to upgrade our app to Angular 6 and create a web component with a custom element, but we need to support IE11 and Edge which do not support native encapsulation, so we would need to test our app in every site where it is used, to make sure they are not breaking our styles, also I don't know whether a web component can manage child routes or not.
Other idea is to use an iframe but my problem here is the iframe resizing to adapt to the content and how to add child routes in the 'host' app from the 'resident' app inside the iframe.
Is there a better way to achieve what we need to do?
The ideal solution should allow our application to be used in multiple sites (each one providing specific configuration) without us having to know about the site using our app.
Thanks for your help.
Answer
UPDATE 2020
You can also use the new Webpack 5 Module federation.
following examples show how to use module federation with Angular and other technologies.
- Implementation examples of module federation , by the creators of module federation
- Example for building a plugin-based workflow designer with Angular and Dynamic Module Federation
- Dynamic Module Federation with Angular
Original answer
I've been very busy with the topic lately, because many have the same problem again and again (me, of course). Nowadays, you often hear the concept of micro-frontends. The concept is about designing the frontend to be extensible and scalable. Especially in the time when many companies have both Angular and React and Vue developers. The following approaches came out of my research:
Links :
You can create your new app and have a hyperlink from your legacy app. (You must have a page reload when you switch beetween the both apps.)
Iframes :
a Software architect builded a meta router to deal with iframes and single page application:
Take a look at this:
Metaframeworks:
Metaframeworks allow you to have a communication beetween
differentsapps builded using differents frameworks:
here some example of metaframeworks for microfrontend purposes.
- Single Spa (official website) Single Spa: a javascript framework for front-end microservices
- FrintJs (official website) FrintJS: Modular JavaScript framework for building Scalable & Reactive applications.
Web Components i.e Angular elements:
In order to deal with npm packages you can use as the other answerer mentioned the concept of Angular elements. You have to create a shell app and another independently apps that will be registred as elements in your shell app. Take a look at this example.: Building micro frontends — angular elements
Mosaiq: Layout service
The online shop Zalando faced to the same problem and created a framework in order to deal with the problem:
- The Mosaic9 https://www.mosaic9.org/
Espacially the part Tailor.js, an open source system for the assembling the components on-demand on a backend layer written in Go.
PS. Tailor was inspired by BigPipe: Pipelining web pages for high performance from Facebook.
Plugin Architecture
A plugin architecture is an architecture that will call external code at certain points without knowing all the details of that code in advance.
This Stackoverflow question explain more about it in case of single page application:
Angular libraries
I Think a right way is to have in a app the same framework and the same version of this framework (e.g Angular 7). I will prefer to take a time a do a upgrade to a typescript version of angular. I hope the answer can be usefull for others.
Other Stackoverflow related Q & A:
Vue.JS - micro frontend approach
Micro frontend architecture advice
Micro frontends examples
- Angular 8 and ReactJS (using NodeJS server and MySQL database): https://github.com/billyjov/angular-react-microfrontend
List of ressources about micro frontends