Showing posts with label angular.io. Show all posts
Showing posts with label angular.io. Show all posts

Thursday, September 7, 2023

Lazy Loading in Angular | Lazy-loading feature modules | Chunk Loading of Components

NgModules are eagerly loaded by default, which means that as soon as the application loads, so do all of the NgModules, whether or not they are immediately required.

Consider lazy loading in angular — a design strategy that loads NgModules as needed — for big apps with many routes. Lazy loading helps to keep initial bundle sizes smaller, which reduces load times.
As Angular generates a SPA (Single Page Application), all of its components are loaded at the same time. This implies that a large number of unneeded libraries or modules may also be loaded.

Lazy loading in angular is the process of loading website components, modules, or other assets when they are needed.
You can utilize lazy loading (or asynchronous loading) with the router if you're constructing your application and utilising feature modules to arrange code. This allows a whole module to load only when needed, reducing the file size of the core bundles and maybe limiting access to bundles to just those who are permitted to use it (like administrative modules).

Because there is no logical isolation if your application has not been split into various modules, lazily loading them into the application is not feasible. The core notion is that the Angular build process can examine code pathways and optimize code depending on how it's used to produce other files, but it relies heavily on Angular modules to know how code is connected.
Steps to Implement Lazy Loading

You need to create your first angular project, you can get help from here how-to-create-multi-layout-application.html

Create a directory under app directory named routes, then create a file under that directory lazy-users-routing.module.ts with below content: 
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

const routes: Routes = [];

@NgModule({
    imports: [RouterModule.forChild(routes)],
    exports: [RouterModule],
})
export class LazyUsersRoutingModule {}


Now create another file in same directory named lazy-user.module.ts with below content: 
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

@NgModule({
    declarations: [ ],
    imports: [
        CommonModule
    ]
})
export class LazyUserModule { }


I assume you have already several component, if not you can create components by your own. Now lets check how we implement Lazy Loading with loadChildren.
Our main routing file app-routing.module.ts will be look like below: 
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import {HomeComponent} from "./modules/home/home.component";
import {DefaultLayoutComponent} from "./layouts/default/default.component";
import {LoginComponent} from "./modules/login/login.component";
import {StaticLayoutComponent} from "./layouts/static/static.component";

const routes: Routes = [
    {
        path: '',
        component: DefaultLayoutComponent,
        children: [
            {
                path: '',
                component: HomeComponent,
            }, {
                path: 'users',
                //component: UsersComponent,
                loadChildren: () => import('./routes/lazy-user.module').then(m => m.LazyUserModule)
            }
        ]
    }, {
        path: '',
        component: StaticLayoutComponent,
        children: [
            {
                path: 'login',
                component: LoginComponent,
            }
        ]
    },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }


This is the main part of app-routing.module.ts file where we enabled lazy loading of our components: 
{
    path: 'users',
    //component: UsersComponent,
    loadChildren: () => import('./routes/lazy-user.module').then(m => m.LazyUserModule)
}


Now we will define UsersComponent in LazyUsersRoutingModule like below: 
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import {UsersComponent} from "../modules/users/users.component";

// This route is prefixed by /users
const routes: Routes = [
    {
        path: '', component: UsersComponent
    }
];

@NgModule({
    imports: [RouterModule.forChild(routes)],
    exports: [RouterModule],
})
export class LazyUsersRoutingModule {}


Our final lazy-user.module.ts is as below: 
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import {UsersComponent} from "../modules/users/users.component";
import {LazyUsersRoutingModule} from "./lazy-users-routing.module";

@NgModule({
    declarations: [
        UsersComponent,
    ],
    imports: [
        CommonModule,
        LazyUsersRoutingModule,
    ]
})
export class LazyUserModule { }


We have enabled lazy loading of component, if we check our network tab we have evidence of that:


GitHub link for this example is https://github.com/pritomkucse/angular-layout/tree/lazy-loading

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Monday, September 4, 2023

How to Create Multi Layout Application with Angular | Angular - Reusable Layout Templates Using Angular Routing | Angular material layout

Angular material provides a layout to create our component inside it; Layout is basically a directive which helps to show or represent the layout for its children. We basically have two types of layouts: flex and grid; angular material provides us inbuild module and directive to create this layout in our application. We all know about the grid layout, and it is very easy to create as well, by the use of a few configurations. We also have few properties that are used to assign the Layout values, and it is mainly as ‘row’ and ‘column’; we can set this parameter some value. Also, we can make the layout responsive by using the Layout property which it is provided. In the coming section of the tutorial, we will have a closer look at the implementation and what changes need to be made in order to run our application properly with detailed examples for beginners.
First, install the Angular CLI, which enables us to download the required packages and library for our project. You can download it by typing the below command on your command make sure you have already installed node see below;
Run command: npm install -g @angular/cli
The above command will install the CLI globally in our system; hence we can use it globally when required.

Now, in this step, we will try to create the new angular project from scratch using routing module using below command

ng new ang1 --routing --defaults

Navigate to project directory then just to make sure, try one command which is mentioned below to install all the required library into our project 
npm install

Will will run below command to run our first angular project: 
ng serve

Out first project is running:
We will continue our second part where we will manage layouts for different types of page, suppose login page will be a clean page where home page page as well as other pages will have left menu enabled. So we will create first layouts here. 1. Default Layout and 2. Static Layout

To do so we will run below commands to create layouts, these 2 commands with create two layouts default and static: 
ng g c layouts/default
ng g m layouts/default
ng g c layouts/static
ng g m layouts/static

Open layouts/static.module.ts and replace StaticModule with StaticLayoutModule, do same for layouts/default.module.ts, replace DefaultModule to DefaultLayoutModule

Open layouts/static.component.ts and replace StaticComponent with StaticLayoutComponent, do same for layouts/default.component.ts, replace DefaultComponent to DefaultLayoutComponent

We will create our componets home and login using below command: 
ng g c modules/home
ng g c modules/login
We will keep app.module.ts as much as simple like below, there will be references to Layouts only rather than components: 
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import {DefaultLayoutModule} from "./layouts/default/default.module";
import {StaticLayoutModule} from "./layouts/static/static.module";

@NgModule({
    declarations: [
        AppComponent,
    ],
    imports: [
        BrowserModule,
        AppRoutingModule,

        DefaultLayoutModule,
        StaticLayoutModule,
    ],
    providers: [],
    bootstrap: [AppComponent]
})
export class AppModule { }

Contents of app/app.component.html: 
<router-outlet></router-outlet>

Contents of app-routing.module.ts: 
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import {HomeComponent} from "./modules/home/home.component";
import {DefaultLayoutComponent} from "./layouts/default/default.component";
import {LoginComponent} from "./modules/login/login.component";
import {StaticLayoutComponent} from "./layouts/static/static.component";

const routes: Routes = [
    {
        path: '',
        component: DefaultLayoutComponent,
        children: [
            {
                path: '',
                component: HomeComponent,
            }
        ]
    }, {
        path: '',
        component: StaticLayoutComponent,
        children: [
            {
                path: 'login',
                component: LoginComponent,
            }
        ]
    },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }

We will create shared component header and footer so that we can use them from any of your component, use below command to create shared components: 
ng g c shared/header
ng g c shared/footer

Shared components are created, now we will create shared module using below command: 
ng g m shared/

We will modify our shared module as below (app/shared/shared.module.ts): 
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import {HeaderComponent} from "./header/header.component";
import {FooterComponent} from "./footer/footer.component";
import {RouterModule} from "@angular/router";

@NgModule({
    declarations: [
        HeaderComponent,
        FooterComponent,
    ],
    imports: [
        CommonModule,
        RouterModule,
    ],
    exports: [
        HeaderComponent,
        FooterComponent,
    ]
})
export class SharedModule { }

Contents of app/shared/header/header.component.html: 
<header>
    <div>
        <a routerLink="/">Home</a>
        <a routerLink="/login">Login</a>
    </div>
</header>

Contents of app/shared/footer/footer.component.html: 
<footer>
    <p>footer works!</p>
</footer>
Lets open app/layouts/default/default.module.ts and keep as below where we import our components (for example home component): 
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import {HomeComponent} from "../../modules/home/home.component";
import {BrowserModule} from "@angular/platform-browser";
import {FormsModule} from "@angular/forms";
import {RouterModule} from "@angular/router";
import {SharedModule} from "../../shared/shared.module";
import {DefaultLayoutComponent} from "./default.component";

@NgModule({
    declarations: [
        DefaultLayoutComponent,
        HomeComponent, //register home component will use this layout
    ],
    imports: [
        FormsModule,
        CommonModule,
        BrowserModule,
        RouterModule,
        SharedModule,//we will access header and footer via shared module
    ]
})
export class DefaultLayoutModule { }

Contents of default.component.html: 
<div class="container-fluid">
    <div class="container-fluid">
        <header class="row">
            <app-header></app-header>
        </header>
        <div id="main" class="row">
            <router-outlet></router-outlet>
        </div>
        <footer class="row">
            <app-footer></app-footer>
        </footer>
    </div>
</div>


Lets open app/layouts/static/static.module.ts and keep as below where we import our components (for example login component): 
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import {StaticLayoutComponent} from "./static.component";
import {LoginComponent} from "../../modules/login/login.component";
import {FormsModule} from "@angular/forms";
import {BrowserModule} from "@angular/platform-browser";
import {RouterModule} from "@angular/router";
import {SharedModule} from "../../shared/shared.module";

@NgModule({
    declarations: [
        StaticLayoutComponent,
        LoginComponent, //register login component will use this layout
    ],
    imports: [
        FormsModule,
        CommonModule,
        BrowserModule,
        RouterModule,
        SharedModule,//we will access header and footer via shared module
    ]
})
export class StaticLayoutModule { }

Contents of static.component.html where we would not include footer and that the way we can differ two layouts default and static: 
<div class="container-fluid">
    <div class="container-fluid">
        <header class="row">
            <app-header></app-header>
        </header>
        <div id="main" class="row">
            <router-outlet></router-outlet>
        </div>
    </div>
</div>
Lets check what we did so far, run command ng serve to start application, below is screenshot of both home and login page where we can clearly seen two different layouts are using.

Home page using default layout where both header and footer available


Login page using static layout where only header available
This is github project link https://github.com/pritomkucse/angular-layout

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