Tree shaking vs Lazy Loading - javascript

In Angular, we can use providedIn: 'root' to make a service tree shakeable. And we can use loadChildren() in our router to specify a lazily loaded module. What's the difference between these two terms 'tree shakeable' and 'lazy loaded'? Do they both only happen when you initially build the project? Why not just call providedIn root services 'lazy loaded services'?

What's the difference between these two terms 'tree shakeable' and 'lazy loaded'?
Tree shaking is a step in a build process that removes unused code from a code base. E.g. components/modules you created, but never used. They get completely eliminated. Same with services, but there are nuances.
Then the code important for the app gets split into bundles by a module bundler. The more lazy loaded elements the app has - the more bundles it will be split into.
Lazy loading means the object will be loaded only when it is needed. E.g. separate lazy-loaded admin module: it has important for the app code, but the code (bundle) won't be sent to ordinary users as they don't have admin permissions, hence they don't need admin-features-related code.
Do they both only happen when you initially build the project?
Yes. During build process unused code gets identified and removed (tree shaking), while the important code gets split into bundles for the purpose of not sending all the app code in one big chunk (including the features the user might not even need). Some of the bundles will be loaded lazily on certain user actions.
Why not just call providedIn root services 'lazy loaded services'?
I presume that providedIn: root services may not be lazy loaded, e.g. the service code will be sent to the user immediately on page init (however the service itself will be initialized on the service usage).

Related

Loading multiple modules under same parent route in Angular

I' am looking for a way through which I can load multiple modules under same path in Angular. For example, consider I have three modules AModule, BModule and CModule each having its own RouterModule.forChild call. Now I want to mount all these modules under say site route.
One way I have achieved this thing is by wrapping routes in RouterModule.forChild call under site route as follows:
RouterModule.forChild([
{
path: 'site',
children: [{}] // children goes here
}
])
I don't know whether this approach is correct but it is working fine. The only issue which this approach is that I have to specify canActivate in every module I want to mount under site. While this is not a problem, I was looking for a cleaner solution.
I know there is a property loadChildren which could be used to load modules lazily. But I want to load modules eagerly.
I' am using AngularCLI which splits code of module I specify in loadChildren in a separate JavaScript file which is not I want.
I' am using AngularClI v1.2.0 and Angular v4.2.5.
Any help is highly appreciated.
Thanks
I'm not entirely clear on your goal and what you are ultimately trying to achieve, but here are a few thoughts.
You can use the loadChildren and "lazy loading" to load on demand OR eagerly. If you select eagerly loaded routes, as soon as your main route is loaded and your first view is displayed, the other modules marked for eager loading are immediately loaded asynchronously.
I have an example of that here: https://github.com/DeborahK/Angular-Routing in the APM-Final folder.
I'm not clear on why you don't want module splitting. It can significantly improve the startup performance (time to display of the first page) of your application.
In addition to canActivate there is also a canActivateChild so you can put this on the parent and not have to repeat it for each route. The docs for that are here: https://angular.io/api/router/CanActivateChild

Angular 2 router config lazy loaded modules

I'm trying to create a service which uses router configuration to create map of routes based on components. It works fine when you don't use lazy loaded module routes.
But I don't know how to get routes from lazy loaded module. In route object there is just loadChildren string and that's it. I digged little bit into angular2 internals and it is using RouterConfigLoader internally to load lazy loaded routes. But it is not exported from RoutingModule, so I suppose it should not be used from the outside.
Is there any public API which would help me with that?
Thanks
But that's the whole idea of lazy loaded modules. No reference exists to the lazy loaded module, so it ain't loaded on load (can I use the word load some more?).
Which also means no routing is available. Based on the string, angular2 loads the (entire) module, and injects the routing on the fly. If you want to know the routing beforehand, you should either not use lazy modules, or do it by hand

angularjs route to controllers from different modules

At the moment we are in the process of creating a new web application infrastructure.
We initially load a dashboard which is esentially the top bar displaying the logged in user and the set of menus along with it. Clicking on each menu would load a screen (mostly crud screens) in the main section. We areplanning to put each of the crud screens and their components (services, controllers and such) in a seperate module which will encapsulate all the screens from each other, so for example if there is 78 screens there will be 78 seperate modules for each screen. We are also using planing on using Requirejs to load these dependencies dynamically.
The problem however occurs that we need to link the menu with each of the modules for each screen. Typically in a single module based app it would be done like this.
config(function($routeProvider, $locationProvider) {
$routeProvider
.when('/Book/load', {
templateUrl: 'book.html',
controller: 'BookController'
})
.when('/Screen/load', {
templateUrl: 'chapter.html',
controller: 'ChapterController'
});
Where the BookController and ChapterController will be in the SAME module.
However in our case the BookController will be in a BookModule for the book screen and the same applies for the ChapterController. And the routes would be in the initial main module for example AppModule which loads the dashboard initially during startup then.
How would we say for example link the AppModule and the routes with each module for each screen (for example in this case BookController and ChapterController) keeping in mind that we need to load the modules dynamically when NEEDED using requirejs.
(P.S : We are essentially segmenting our application based on feature where feature in our system usually equals screen)
Also any suggestions on any other way we could best structure our app including an answer to the above problem would be very much appreciated.
Regards,
Milinda
Why do you have the route configuration in the initial main module? This creates unnecessary coupling between your modules (ie. your initial module has to know all the possible routes of every module), sort of defeating the purpose of moving your code into modules in the first place.
Each of your modules can have their own route configuration, which will take effect when the modules are loaded. (A consistent naming convention can help avoiding clashes between routes of unrelates modules)
While configuring the routeProvider, you can use lazy loading mechanisms using the resolve attribute of routes: resources referenced here will be resolved before the routeChange event happens, which enables you to wait for any promise resolution or a requireJS loading of a file. This blogpost might help in that regard.
As of this moment, there is no mechanism as far as I am aware for dynamically loading modules at runtime and then incorporating them in an AngularJS app. You can breakdown your app into 78 individual modules loaded via requirejs, but you will still need a single primary module which has all those other 78 as dependencies. It is this primary module which you will then configure all the routes.
There is work going on into a new AngularJS router which borrows from other more flexible routers (i.e. ui-router, etc) which will allow exactly the sort of dynamic loading of modules you are speaking about but as far as I know it won't be available until AngularJS 1.4.

React, async loading for multiple sections/views with different components

I'm having an issue thinking about the best way to architect a React app with multiple pages/views (still a SAP).
Let's say we have a simple app with 4 major sections (pages): dashboard, users, stats, comments. Each section has different components in it (think react components). For example, the comments section would have a hierarchy like so:
CommentsSection
- CommentsQueue
-- Comment
--- Text
--- Buttons
- CommentsApproved
--Comment
--- Text
--- Buttons
In a framework like angular for example, the 4 main sections would be split into partials, and loaded in an ng-view upon request, with their respective components inside. When landing on the homepage, the app would only load the dashboard view and upon the user clicking on a nav item, the selected route (i.e. app/users or app/users/:id) would trigger and the app will load the required "template-view-partial" (without a browser refresh).
Now in terms of React, how would this occur? it seems like ALL views and ALL their components would need to be available in a browserified JS file and the app can then update the DOM.
This seems terribly wrong, as we'd be loading all sections in the first load, even if the user doesn't ever need to get to that section. Granted, we could split it with routes on the server, and only serve the components for the page based on the route, but that would require a browser refresh, where as in Angular for example, it would happen without a browser refresh as the view is loaded asynchronously.
The question is, how can this asynchronous loading happen in a React-based app?
I think there's a few different ways in approaching this, I'll explain the approach that I am currently using for my work and side projects.
Instead of using browserify, we use a module-bundler called webpack (https://github.com/webpack/webpack). What's great about webpack is that it's like Browserify but can split your app into multiple 'bundles'. This is great because if we have multiple components/views, the user would just download the features they need for that particular view without having to download everything initially. It allows react-components and their dependencies to be downloaded on demand.
Pete Hunt wrote an article that goes into depth on the benefits of webpack when using it with React (including how to async load react components), and how it is similar/different to Browserify and modern build tools like Grunt/Gulp: https://github.com/petehunt/webpack-howto
I have described one solution using webpack here : http://blog.netgusto.com/asynchronous-reactjs-component-loading-with-webpack/
In essence :
use require.ensure([], cbk) to define code chunks; in the cbk, load your packages synchronously using require()
in your host component, load your asynchronous component in componentWillMount(), and set in in the host component state.
use it in the host component render, when defined on the state

Advice on requirejs dynamic loading of modules or use optimization/bundle tool in my situation

I'm building a new web application that will consist of totally different interfaces/user experiences depending on what TYPE of user has just authenticated/logged in. Lets call these users Admins & Delegates.
Admins and Delegates have completely different functionality in this application. Only a small subset of my modules will be used by both. It's essentially two different client applications hooked up to my backend.
Should I create two different build files with the RequireJS optimizer, and then inject either of them into the page depending on what the server returns when the user performs a login? Or should I focus more on requirejs's dynamic module loading and just load the modules I need when I need them (thus running into a lot of extra http requests :/)
We have a Backbone app, that shares a lot of views and models, but not all clients have all navigation points, and some models behave differently.
So first we have a single require entry point and a single require.config for every client.
Bootstrap-client1.js
requirejs.config({
baseUrl: 'js/cfe/app',
paths: {
'common/ViewA': 'clients/client1/ViewA',
'common/ModelB': 'clients/client1/ModelB',
'common/ColletionC': 'clients/client1/CollectionC'
}
});
requirejs([
'common/App',
'common/BaseSetup'],
function(app, BaseSetup) {
$(function() {
BaseSetup.start();
app.start();
});
}
);
So later on when we use a shared View that requires ModelB this will replaced with our client1/ModelB implementation.
For production we build a single compiled version for every client with the r compiler and change the source of the data-main attribute in the html file when the client request the html file.

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