Micro Front-Ends

MICRO FRONT-ENDS
Ori Calvo
Trainologic

2
Technology evolves quickly
 Backbone, Knockout, Ember, Meteor, AngularJS …
 React, Angular, VueJS …
 We can build awesome apps with AngularJS
 Would you join a company that only uses AngularJS ?

3
Front-end gets bigger
 Migrating to latest technology stacks takes time
 The big bang approach is not practical

4
End-to-End teams
 VS. technical teams
 Each team delivers separately
 Each team has its own opinion …

5
Micro Front-Ends Approach
“Recipes for building a web app with multiple teams using
different JavaScript frameworks”
https://micro-frontends.org/
Michael Geers

6
Who am I
 Ori Calvo
 Head of Front end technologies @ Trainologic
 Over 20 years of development/leading experience
 Manager of the WDCIL Meetup group
 Owner of the extremely popular t-rex library

7
Tomorrow Seminar
 Building Reusable Web Components
 Gil Fink

8
Recipes
 Multiple SPAs at different URLs
 Web components
 IFrames
 Shared event bus
 Layout service
 The single-spa framework

9
Multi SPAs
 Each SPA lives in its own URL
 Probably the easiest solution 
 Not so great UX 
 Use a reverse proxy to simplify navigation

10
Multi SPAs - DEMO
 window.open
 Set a gateway
 Shared app store
 Shared API

11
Multi SPAs - More
 Shared infra can be moved to a dedicated NPM package
 Can use window.opener to share state & API
 Switching between existing tabs is tricky
 Many opened tabs  Performance issues

12
single-spa Meta-framework
 Hosts multiple applications inside single SPA
 Implements a cross application router
 Only one active at a time
 Each application is associated with a router prefix
 Each application must support: bootstrap, mount, unmount

14
index.html
<body>
<script src="/dist/common-dependencies.js"></script>
<script src="/dist/root-application.js"></script>
<div class="navbar">
<ul>
<a onclick="singleSpaNavigate('/app1')"><li>App 1</li></a>
<a onclick="singleSpaNavigate('/app2')"><li>App 2</li></a>
</ul>
</div>
<div class="app1"></div>
<div class="app2"></div>
</body>

15
Root App
import * as singleSpa from 'single-spa';
singleSpa.registerApplication('app1',
() => import ('./app1/main.js'),
location => location.pathname.startsWith(`/app1`));
singleSpa.registerApplication('app2',
() => import ('./app2/main.js'),
location => location.pathname.startsWith(`/app2`));
singleSpa.start();

16
React
const reactLifecycles = singleSpaReact({
React,
ReactDOM,
rootComponent: Root,
domElementGetter: () => document.querySelector("body > .app1"),
});
export function bootstrap(props) {
return reactLifecycles.bootstrap(props);
}
export function mount(props) {
return reactLifecycles.mount(props);
}
export function unmount(props) {
return reactLifecycles.unmount(props);
}

17
Angular
const ngLifecycles = singleSpaAngular({
domElementGetter: () => document.querySelector("body > .app2"),
mainModule: AppModule,
angularPlatform: platformBrowserDynamic(),
template: `<app-root></app-root>`,
})
export function bootstrap(props) {
return ngLifecycles.bootstrap(props);
}
export function mount(props) {
return ngLifecycles.mount(props);
}
export function unmount(props) {
return ngLifecycles.unmount(props);
}

18
single-spa
 All major FX are supported
 Does not help with component interaction
 Need to manually configure a webpack build
 Use React/Angular eject
 Mounting & unmounting are heavy operations

19
The Web Components Standard
 HTML imports
 HTML templates
 Custom elements
 Shadow DOM

20
Custom Element
class MyClock extends HTMLElement {
constructor() {
super();
}
connectedCallback() {
this.innerText = new Date();
}
}
customElements.define('my-clock', MyClock);

22
Web Components
 Maintain a single SPA
 Use custom elements as integration layer
 Each component is wrapped inside a custom element
 Internally you may use whatever FX you want

24
Web Components
 Probably another wrapper is required
 Per host application type 
 Custom element supports attributeChangedCallback
 However, attribute must be a string
 Versioning
 Loading two React/Angular instances is tricky
 Stencil
 Angular Elements

25
IFrames
 Quite similar to the “Multi SPA” approach
 Allows for component interaction
 Over application interaction
 However,
 Scrollbar is a nightmare
 CSS does not cascade easily
 Cannot nest too much
 Bundle size

26
Layout Service
 Project Mosaic at https://www.mosaic9.org/
 Offers Tailor layout service
 Composing a website out of various Fragments
 Inspired by Facebook’s BigPipe

27
Summary
 Lots of recipes and small tools
 No significant leader
 single-spa is probably the most famous
 Should resemble the organization layout

THANK YOU
Ori Calvo
Trainologic

Micro Front-Ends

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