Selector of Type
The HTML tag name is the basis for selects. App-root as an example. Since this kind of selection is the standard for all Angular components, you probably already know it.

Attribute Selector

• The selector property in the @Component decorator specifies the selector for the component. In this case, we're using an attribute selector [app-attribute-selector].
• To use the directive, you add the app-attribute-selector attribute to any HTML element in your template.
• The content within that element will be replaced by the template defined in the directive.

import { Component } from '@angular/core';

    @Component({
      selector: '[app-attribute-selector]',
      standalone: true,
      imports: [],
      templateUrl: './attribute-selector.component.html',
      styleUrl: './attribute-selector.component.scss'
    })
    export class AttributeSelectorComponent {

    }

component view code
<p>attribute-selector works!</p>

Attribute selector with value

• The selector property in the @Component decorator specifies the selector for the component. In this case, we're using an attribute selector [app-attribute-selector-with-value=” test”].
• To use the directive, you add the app-attribute-selector-with-value=” test” attribute to any HTML element in your template.
• The content within that element will be replaced by the template defined in the directive.

    import { Component } from '@angular/core';

    @Component({
      selector: '[app-attribute-selector-with-value="test"]',
      standalone: true,
      imports: [],
      templateUrl: './attribute-selector-with-value.component.html',
      styles: ``
    })
    export class AttributeSelectorWithValueComponent {

    }

component view code
<p>attribute-selector-with-value works!</p>

The selector with multiple attributes
The selector property in the @Component decorator specifies the selector for the component. In this case, we're using an attribute selector [app-multiple-attribute-selector="test"][is-active].
To use the directive, you add the app-multiple-attribute-selector="test" is-active attribute to any HTML element in your template.
The content within that element will be replaced by the template defined in the directive.
    import { Component } from '@angular/core';

    @Component({
      selector: '[app-multiple-attribute-selector="test"][is-active]',
      standalone: true,
      imports: [],
      templateUrl: './multiple-attribute-selector.component.html',
      styleUrl: './multiple-attribute-selector.component.scss'
    })
    export class MultipleAttributeSelectorComponent {

    }

component view code
<p>multiple-attribute-selector works!</p>

Key Points
Attribute selectors are useful when you want to apply a component to multiple elements based on a common attribute.
They are often used for directives that provide additional functionality to existing elements.
Attribute selectors are case-sensitive.

Note. For attribute values, Angular supports matching an exact attribute value with the equals (=) operator. Angular does not support other attribute value operators.
CSS Class Selector
 
Class selector
A CSS class selector is used to target elements that have a specific class attribute. The class attribute is defined within the opening tag of an HTML element and is preceded by a dot (.).
import { Component } from '@angular/core';

@Component({
  selector: '.app-css-class-selector',
  standalone: true,
  imports: [],
  templateUrl: './css-class-selector.component.html',
  styles: ``
})
export class CssClassSelectorComponent {

}

component view code
<p>css-class-selector works!</p>

:not pseudo-class
The: not pseudo-class in CSS allows you to target elements that do not match a specific selector. You can leverage this in Angular component selectors to create more targeted components.

Explanation

• The :not(.disabled) part of the selector ensures that the component only matches elements with the class "container" that do not also have the class "disabled".
• This provides a way to conditionally apply the component based on the presence or absence of other classes.

    import { Component } from '@angular/core';

    @Component({
      selector: '.app-css-not-pseudo-selector:not(.disabled)',
      standalone: true,
      imports: [],
      templateUrl: './css-not-pseudo-selector.component.html',
      styles: ``
    })
    export class CssNotPseudoSelectorComponent {

    }

component view code
<p>css-not-pseudo-selector works!</p>

Targeting elements that are not direct children of a specific element.
@Component({
  selector: 'div:not(.parent) > p'
})
export class MyComponent {
}

Targeting elements that do not have a specific attribute.
@Component({
  selector: 'button:not([disabled])'
})
export class MyButtonComponent {
}

Key Points

• The :not pseudo-class can be combined with other selectors to create more complex targeting rules.
• It's a powerful tool for creating reusable components that can be applied conditionally based on the structure of your HTML.
• Be cautious when using :not with complex selectors, as it can sometimes lead to unexpected behavior if not used correctly.

By understanding and utilizing the : not pseudo-class, you can create more flexible and targeted components in your Angular applications.

Combining selectors
You can combine selectors in Angular using CSS-like syntax to create more specific targeting rules. Here are some examples.
You can combine with Element, class, id, pseudo-class, attributes, comma-separated selectors, and so on.

Combining by Element, Class, and ID
@Component({
  selector: 'div.container#my-container'
})
export class MyComponent {
}

This component will only match elements that are.

• A div element
• Have the class container
• Have the ID my-container

Combining with Pseudo-Classes
TypeScript
@Component({
  selector: 'button:not(.disabled):hover'
})
export class MyButtonComponent {
}

This component will match buttons that.

• Do not have the class disabled
• Are being hovered over

Combining with Attributes
TypeScript
@Component({
  selector: '[data-type="product"][is-active]'
})
export class ActiveProductComponent {
}

This component will match elements that.

• Have the attribute data type with the value "product"
• Have the attribute is-active

Combining Multiple Selectors

You can combine multiple selectors using commas.
TypeScript
@Component({
  selector: '.container, .card'
})
export class MyComponent {
}

This component will match elements that have either the class container or the class card.

Remember

• Specificity: The more specific your selector is, the higher its priority.
• Cascading Stylesheets (CSS): If multiple selectors match an element, the most specific selector takes precedence.
• HTML Structure: Ensure that your selectors match the structure of your HTML elements.

By effectively combining selectors, you can create targeted components that accurately match the elements you intend to interact with in your Angular application.

Below is the output of the Selectors explained above.
    App.component.ts

    import { Component } from '@angular/core';
    import { RouterOutlet } from '@angular/router';
    import { AttributeSelectorComponent } from './attribute-selector/attribute-selector.component';
    import { MultipleAttributeSelectorComponent } from './multiple-attribute-selector/multiple-attribute-selector.component';
    import { AttributeSelectorWithValueComponent } from './attribute-selector-with-value/attribute-selector-with-value.component';
    import { CssClassSelectorComponent } from './css-class-selector/css-class-selector.component';
    import { CssNotPseudoSelectorComponent } from './css-not-pseudo-selector/css-not-pseudo-selector.component';
    import { CombiningSelectorsComponent } from './combining-selectors/combining-selectors.component';

    @Component({
      selector: 'app-root',
      standalone: true,
      imports: [
        RouterOutlet,
        AttributeSelectorComponent,
        MultipleAttributeSelectorComponent,
        AttributeSelectorWithValueComponent,
        CssClassSelectorComponent,
        CssNotPseudoSelectorComponent,
        CombiningSelectorsComponent
      ],
      templateUrl: './app.component.html',
      styleUrl: './app.component.scss',
    })
    export class AppComponent {
      show = false;
      testId = 'main-cta';
      title = 'angular-dev-test';
    }

component view code
@if(show){
<button [attr.data-test-id]="testId">Show CTA</button>
} @else {
<button [attr.data-test-id]="testId">Normal CTA</button>
}

<div app-attribute-selector is-active>will be ignored</div>
<div app-attribute-selector-with-value="test">will be ignored</div>
<div app-multiple-attribute-selector="test" is-active>will be ignored</div>
<div class="app-css-class-selector">will be ignored</div>
<div class="app-css-not-pseudo-selector">will be ignored</div>
<button type="reset">Reset</button>

Page Output

The route guards provided by Angular are effective tools for controlling access control inside your application. They improve security and user experience by assisting in making sure that users can only access routes that they are permitted to view. Poorly designed route guards, however, might cause security flaws and performance snags as your program expands. In order to successfully balance performance and security, we'll look at advanced ways for improving Angular route guards in this post.

1. Understanding Angular Route Guards
Angular offers several types of route guards, each serving a specific purpose.

• CanActivate: Determines if a route can be activated.
• CanDeactivate: Determines if the user can navigate away from the current route.
• CanActivateChild: Checks if a child route can be activated.
• CanLoad: Determines if a lazy-loaded module should be loaded.
• Resolve: Fetches data before a route is activated.

2. Route guards and lazy loading
By loading modules only when necessary, lazy loading is a crucial strategy for enhancing the efficiency of large Angular applications. Nevertheless, these advantages can be circumvented by using lazy-loaded modules in conjunction with route guards incorrectly.

Best Practices

• Use CanLoad Instead of CanActivate for Lazy-Loaded Modules: The CanLoad guard prevents the entire module from loading if the guard returns false. This is more efficient than CanActivate, which loads the module but prevents activation if conditions aren’t met.
• Preload Critical Modules: Use Angular's built-in preloading strategies, such as PreloadAllModules, to preload essential modules, ensuring quick access without sacrificing performance.

canLoad(route: Route): boolean {
  return this.authService.isLoggedIn();
}

3. Reducing Overhead in CanActivate Guards
CanActivate guards are commonly used to restrict access to routes based on user authentication or roles. However, performing complex logic or redundant checks in these guards can slow down navigation.

Best Practices

• Cache User Permissions: Instead of fetching permissions from the server on each route change, cache them locally using services like NgRx or simple in-memory storage. Update the cache only when necessary (e.g., on login or role change).
• Optimize Guard Logic: Ensure that the logic within your CanActivate guards is as efficient as possible. Avoid making unnecessary HTTP requests or performing complex calculations synchronously.
• Asynchronous Guard Execution: Use asynchronous operations in guards only when necessary. When using Observable or Promise-based guards, ensure that they resolve quickly to avoid delays in route transitions.

canActivate(route: ActivatedRouteSnapshot): boolean {
  const requiredRole = route.data['role'];
  return this.authService.hasRole(requiredRole);
}

4. Enhancing Security with Role-Based Access Control (RBAC)Implementing RBAC within your route guards is a robust way to enforce security policies across your application. However, a poorly designed RBAC system can lead to security loopholes.Best Practices

• Centralize Role Management: Manage user roles and permissions in a centralized service. This makes it easier to update and audit roles across your application.
• Dynamic Role Assignment: Assign roles dynamically based on user data rather than hardcoding roles within your application. This allows for more flexible and maintainable access control.
• Audit Route Guard Usage: Regularly audit your route guards to ensure that they are correctly implemented and up-to-date with your security policies. This helps prevent unauthorized access due to outdated or misconfigured guards.

canActivate(route: ActivatedRouteSnapshot): boolean {
  const requiredRoles = route.data['roles'] as Array<string>;
  return this.authService.hasAnyRole(requiredRoles);
}

5. Combining Multiple Guards Efficiently
In some cases, you may need to combine multiple guards for a single route. For example, you might want to check if a user is authenticated and if they have a specific role.

Best Practices
Use Composite Guards: Instead of chaining multiple guards, create composite guards that encapsulate all necessary checks. This reduces the overhead of multiple guard evaluations.

canActivate(route: ActivatedRouteSnapshot): boolean {
  return this.authService.isLoggedIn() && this.authService.hasRole('admin');
}

Order Guards for Efficiency: If you must use multiple guards, order them from least to most computationally expensive. This ensures that simple checks are performed first, potentially bypassing more complex checks if they fail.
const routes: Routes = [
  {
    path: 'admin',
    canActivate: [AuthGuard, RoleGuard],
    component: AdminComponent
  }
];

6. Debugging and Testing Route Guards
Even with optimizations, route guards can introduce issues if not thoroughly tested and debugged.

Best Practices

• Unit Testing Guards: Write unit tests for your route guards to ensure they behave as expected under various conditions. Use Angular's TestBed to create isolated tests for each guard.
• Logging and Monitoring: Implement logging within your guards to monitor their execution in production. This can help identify performance bottlenecks or security issues that may arise.
• Profiling Route Guards: Use Angular’s built-in profiling tools or browser developer tools to measure the performance impact of your route guards. Optimize any guards that are identified as slow or resource-intensive.

it('should allow the authenticated user to access route', () => {
  authService.isLoggedIn.and.returnValue(true);
  expect(guard.canActivate()).toBe(true);
});

Conclusion
Optimizing Angular route guards for performance and security requires a deep understanding of Angular’s routing system and careful consideration of best practices. By implementing lazy loading strategies, reducing overhead in guard logic, enhancing security with RBAC, and efficiently combining multiple guards, you can ensure that your Angular application is both fast and secure.

You will discover the solutions to the following questions and how to transfer/share data from the child component to the parent component in this walkthrough.

• @Output: What is it?
• An Event Emitter: What Is It?

  

What is @Output?
@Output decorator is used to share the data from the child component to the parent component.

What is an event emitter?
An event emitter is used to create custom events for AngularComponent. Mainly, the event emitter is used to pass data from a child component to a parent component using the @output decorator.

In short, sending data to the parent is publishing /emitting the vent, and the parent component listens the same.

Send Data from Child to Parent Component
Create an Angular Project called “AnguWalk” using the following CLI command.

Command
ng new AnguWalk

Example

Move the cursor to inside the project folder and open Visual Studio code.

Command
cd anguwalk <enter>
code . <enter>

Example

Note. Visual studio code will get started only if your system is configured with path and settings.
Now, we are going to Create a child component to issue the default city value.

Command
ng g c childdefacity

Open the childdefacity.component.ts file and update the following code.
import { Component, EventEmitter, OnInit, Output } from '@angular/core';

@Component({
  selector: 'app-childdefacity',
  standalone: true,
  imports: [],
  templateUrl: './childdefacity.component.html',
  styleUrls: ['./childdefacity.component.css']
})
export class ChilddefacityComponent implements OnInit {
  defaultcity: string = "Shirdi";
  @Output() updatecity = new EventEmitter<string>();
  ngOnInit(): void {}
  SendToParent() {
    this.updatecity.emit(this.defaultcity);
  }
}

Open the childdefacity.component.html file and update the following code.
<p>Child Component Content --> childdefacity works!</p>
<button type="button" style="font-size: xx-large;" (click)="SendToParent()">Send Default City</button>

Open the app.component.ts file and update the following code.
import { Component, NgModule, OnInit } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { CommonModule } from '@angular/common';
import { RouterOutlet } from '@angular/router';
import { ChilddefacityComponent } from './childdefacity/childdefacity.component';
declare function HelloMsg(arg: any): void;
@Component({
  selector: 'app-root',
  standalone: true,
  imports: [RouterOutlet, FormsModule, CommonModule, ChilddefacityComponent],
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  parentdefacity: string = '';
  txtFullname: string = '';
  txtCityname: string = '';

  getdata(defacity: string) {
    this.txtCityname = defacity;
    // alert(this.txtCityname);
  }
  formpro(form: any) {
    alert('submit');
    console.log(form);
    console.log(this.txtCityname);
    console.log(this.txtFullname);
  }
}

Open the app.component.ts file and update the following code.
import { Component, NgModule, OnInit } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { CommonModule } from '@angular/common';
import { RouterOutlet } from '@angular/router';
import { ChilddefacityComponent } from './childdefacity/childdefacity.component';
declare function HelloMsg(arg: any): void;
@Component({
  selector: 'app-root',
  standalone: true,
  imports: [RouterOutlet, FormsModule, CommonModule, ChilddefacityComponent],
  templateUrl: './app.component.html',
  styleUrl: './app.component.css'
})
export class AppComponent {
  parentdefacity: string = "";
  txtFullname: string = "";
  txtCityname: string = "";

  getdata(defacity: string) {
    this.txtCityname = defacity;
    // alert(this.txtCityname);
  }
  formpro(form: any) {
    alert("submit");
    console.log(form);
    console.log(this.txtCityname);
    console.log(this.txtFullname);
  }
}

Open the app.component.html file and update the following code.
<router-outlet />

<form #contForm="ngForm" (ngSubmit)="formpro(contForm.value)">
  <table>
    <tr>
      <td>Fullname</td>
      <td>
        <input
          type="text"
          id="txtFullname"
          style="font-size: xx-large;"
          name="txtFullname"
          [(ngModel)]="txtFullname">
      </td>
    </tr>

    <tr>
      <td>City</td>
      <td>
        <input
          type="text"
          id="txtCity"
          style="font-size: xx-large;"
          name="txtCity"
          [(ngModel)]="txtCityname">
      </td>
    </tr>

    <tr>
      <td colspan="2">
        <app-childdefacity (updatecity)="getdata($event)"></app-childdefacity>
      </td>
    </tr>

    <tr>
      <td colspan="2">
        <button type="submit" style="font-size: xx-large;">Submit</button>
      </td>
    </tr>
  </table>
</form>

OUTPUT

React and Angular are two of the most widely used front-end frameworks for creating contemporary online apps. Both are supported by sizable groups and have distinct advantages, yet they serve varying needs and tastes. We'll go over the main distinctions between Angular and React in this post to assist you in choosing the right framework for your project.

Overview

1. React
   • Developed by: Facebook
   • Initial Release: 2013
   • Type: JavaScript library for building user interfaces, primarily focused on rendering UI components.
   • Learning Curve: Moderate
   • Main Concept: React is centered around components and follows a unidirectional data flow.
2. Angular
   • Developed by: Google
   • Initial Release: 2016 (as Angular 2, the complete rewrite of AngularJS)
   • Type: Full-fledged framework for building web applications.
   • Learning Curve: Steep
   • Main Concept: Angular is an opinionated framework that provides a comprehensive solution for building large-scale applications, including built-in features like routing, state management, and HTTP services.

Architecture

1. React
   • Component-Based: React is all about components. Each piece of UI is a component that can manage its state and be reused throughout the application.
   • Virtual DOM: React uses a virtual DOM to optimize rendering performance. When the state of a component changes, React updates the virtual DOM and then efficiently updates the real DOM.
   • Flexibility: React offers flexibility by allowing developers to choose their own libraries for routing, state management, and other needs. This makes React a "view library" rather than a full-fledged framework.
2. Angular
   • MVC Architecture: Angular follows the Model-View-Controller (MVC) pattern, which helps in separating the concerns of data (Model), UI (View), and logic (Controller).
   • Real DOM: Unlike React, Angular directly interacts with the real DOM, which can impact performance in complex applications. However, Angular mitigates this with its change detection mechanism.
   • Built-In Features: Angular comes with a range of built-in features like form validation, HTTP client, routing, and RxJS for reactive programming. This makes Angular a complete solution for building applications without relying on external libraries.

Performance

1. React
   • Virtual DOM: React’s virtual DOM significantly improves performance by minimizing the number of direct manipulations to the real DOM.
   • Component Reusability: React’s component-based architecture promotes reusability, which can lead to better performance in large applications.
   • Bundle Size: React itself is relatively lightweight, but depending on the additional libraries you use, the bundle size can grow.
2. Angular
   • Change Detection: Angular’s change detection mechanism can sometimes lead to performance bottlenecks in large applications, but it also provides tools like OnPush strategy and NgZone to optimize performance.
   • Ahead-of-Time (AOT) Compilation: Angular’s AOT compilation improves performance by compiling the application during the build process, reducing the load time.
   • Built-In Features: While Angular’s rich feature set can impact performance, the framework’s ability to optimize these features mitigates the impact.

Learning Curve

1. React
   • JSX: React uses JSX, a syntax extension that allows you to write HTML within JavaScript. While some developers find JSX intuitive, others might find it challenging initially.
   • Flexibility: React’s flexibility means you need to learn how to integrate and use various libraries for routing, state management, etc., which can be both an advantage and a challenge.
   • Documentation and Community: React has extensive documentation and a large community, making it easier to find resources, tutorials, and third-party libraries.
2. Angular
   • Steep Learning Curve: Angular has a steeper learning curve due to its complexity and the number of built-in features you need to understand.
   • TypeScript: Angular is built with TypeScript, a statically typed superset of JavaScript. While this adds benefits like better tooling and error checking, it also requires learning TypeScript if you’re not already familiar with it.
   • Comprehensive Framework: Angular’s opinionated nature means that once you learn the Angular way of doing things, you have a powerful set of tools at your disposal.

Ecosystem and Community

1. React
   • Ecosystem: React has a rich ecosystem with numerous libraries for state management (Redux, MobX), routing (React Router), and more. The flexibility to choose different tools gives developers more control over their stack.
   • Community: React has a large and active community, contributing to a vast array of plugins, tools, and resources.
2. Angular
   • Ecosystem: Angular has a more integrated ecosystem. Many features that require third-party libraries in React are built into Angular, such as routing, HTTP services, and form handling.
   • Community: Angular also has a large community, but it is more centralized around the official Angular resources, documentation, and Google-backed initiatives.

Use Case
React

1. When to Use React
   • You need flexibility in choosing libraries and tools.
   • You prefer a simple, component-based architecture.
   • You are building a project where performance and simplicity are key.
2. Popular Use Cases
   • Single-page applications (SPAs)
   • Static sites with dynamic components
   • Dashboards and data visualization tools

Angular

1. When to Use Angular
   • You are building a large-scale, enterprise-level application.
   • You need a framework with a comprehensive set of tools and built-in features.
   • You prefer an opinionated framework that guides architectural decisions.
2. Popular Use Cases
   • Complex, enterprise-level applications
   • Applications requiring robust form handling and validation
   • Real-time applications with complex state management

Conclusion
The skills of your team and the needs of your project will determine which of React and Angular is best. React is an excellent option for projects where you want more control over the architecture because of its simplicity and versatility. In contrast, Angular offers a feature-rich, opinionated framework right out of the box, making it perfect for enterprise-level apps.

Both Angular and React are effective front-end development tools, and knowing the advantages and disadvantages of each will help you choose wisely for your upcoming project.

In Angular, component routing is usually done via the Router service. This allows you to call or go to a component from another component. Here's how you can make this happen. In the Router Module, define routes. The first step is to configure your routes in your AppRoutingModule (or any other defined routing module). Describe the pathways and the matching parts.

import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import { ComponentA } from './component-a/component-a.component';
import { ComponentB } from './component-b/component-b.component';

const routes: Routes = [
  { path: 'component-a', component: ComponentA },
  { path: 'component-b', component: ComponentB },
  // Add more routes as needed
];

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

Use RouterLink in Templates
You can navigate to another component using the RouterLink directive in your template (HTML) of the first component.
<!-- component-a.component.html -->
<a [routerLink]="['/component-b']">Go to Component B</a>

Navigate Programmatically Using the Router
You can also navigate programmatically using the Angular Router in your component's TypeScript file.
import { Component } from '@angular/core';
import { Router } from '@angular/router';

@Component({
  selector: 'app-component-a',
  templateUrl: './component-a.component.html',
  styleUrls: ['./component-a.component.css']
})
export class ComponentA {

  constructor(private router: Router) { }

  goToComponentB() {
    this.router.navigate(['/component-b']);
  }
}

In HTML template
<!-- component-a.component.html -->
<button (click)="goToComponentB()">Go to Component B</button>

Outlet to Render Routed Components
Ensure you have a <router-outlet></router-outlet> in your main HTML template (e.g., app.component.html) where the routed components will be displayed.
<!-- app.component.html -->
<router-outlet></router-outlet>

Lazy Loading (Optional)
If you want to load a module lazily, define your route like this.
const routes: Routes = [
  {
    path: 'component-b',
    loadChildren: () =>
      import('./component-b/component-b.module')
        .then(m => m.ComponentBModule)
  }
];

Summary

• RouterLink: For navigation within the template.
• Router.navigate: For programmatic navigation within the component's TypeScript file.
• Router Outlet: Acts as a placeholder in the template where routed components are displayed.

This setup allows you to call or navigate between components effectively in Angular.

Increasing the speed and smoothness of an application requires performance tuning. To aid in this, Angular, a well-liked framework for creating online applications, has introduced the @defer directive. Both load times and user experience are enhanced. We'll explain the @defer directive, its operation, and how you can use it to improve your Angular apps in this blog post.

@defer: What is it?

Using an Angular condition, the @defer directive allows you to load specific portions of a template only when needed. This can improve the efficiency of your program by only rendering components when required. For instance, it can load and display material only after the user presses a button or until a certain portion of the screen is visible. In this manner, your software loads faster and more effectively because it just loads what is needed.

Syntax
@defer () {
} @placeholder () {
} @loading () {
} @error {
}

@defer Directive
This is used to delay the loading of a template fragment until certain conditions are met.
on <trigger>: Specifies an event that triggers the deferred loading. Here is one simple example of on viewport trigger

@defer (on viewport) {
  <component />
}

(on viewport) specifies that the deferred rendering should happen when the element comes into the viewport.

when <condition>: Defines the condition that needs to be true before the template is loaded.
prefetch on <trigger>: Optionally, you can prefetch the content based on a trigger.
prefetch when <condition>: Optionally, you can prefetch the content when a certain condition is true.

@placeholder Directive
This defines what should be shown while the deferred content is being loaded.

@loading Directive
This defines the content to be shown while the deferred content is actually loading.

@error Directive
This defines what should be shown if there's an error during the loading process.

In short, this syntax lets you control when different parts of your Angular template appear and what to show while you’re waiting, depending on different conditions and triggers.

Benefits of Using @defer directive

• Faster Loading: By delaying less important content, your app loads quicker and feels smoother to use.
• Better User Experience: Users see the key parts of your app right away, while the less important stuff loads in the background, so the app stays responsive.
• Efficient Use of Resources: By waiting to display parts of your app that aren’t needed right away, you free up your browser’s resources, making everything run more smoothly.

Summary
The @defer directive in Angular helps make your app run better and faster. It allows you to delay loading some parts of your app until they're really needed. This way, your app stays quick and responsive, even if it has a lot of data or complex tasks. Using @defer can make your app perform better and provide a smoother experience for users.

Please let me know in the comments area if you have any questions.

One of the most useful features of an Angular application is the ability to manage route access with Angular Guards. They aid in application security by deciding whether or not a user can access a specific route. An in-depth explanation of angular guards, including their types, applications, and real-world examples, will be given in this article.

Angular Guard Types
Angular offers five different kinds of guards.

• CanActivate: Ascertains the possibility of activating a route.
• CanActivateChild: Ascertains whether it is possible to activate a child route.   
• CanDeactivate: Ascertains if deactivating a route is possible.
• Before a route is activated, resolve pre-fetches of data.
• Checks whether a module can be loaded slowly using the CanLoad function.

Angular can do more with routing than just rendering components. Large-scale applications can work and perform much better with advanced routing systems. I'll go over some of the more intricate features of Angular's Router here, such as nested routes, route guards, and lazy loading.

1. Lazy Loading
Lazy loading is a technique to load JavaScript components asynchronously when they are needed rather than loading everything upfront. This is particularly useful for large applications with numerous features, reducing the initial load time and improving performance. To implement lazy loading in Angular, you can define routes to load modules only when they are accessed.

Example
Suppose you have a feature module named AdminModule which you want to load only when needed. First, you'll need to create a routing module for AdminModule.

// admin-routing.module.ts
import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { AdminComponent } from './admin/admin.component';
const routes: Routes = [
  { path: '', component: AdminComponent }
];
@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule]
})
export class AdminRoutingModule { }

Then, update the main routing module to lazy load AdminModule.
// app-routing.module.ts
import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
const routes: Routes = [
  { path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule) }
];
@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }

2. Route Guards
Route guards are useful for granting or restricting access to certain routes based on specific conditions, such as user authentication or authorization. Angular provides several types of route guards including CanActivate, CanActivateChild, CanDeactivate, and Resolve.

Example
Here’s how you can use a CanActivate guard to prevent access to a route for unauthenticated users.

First, implement the CanActivate interface.
// auth.guard.ts
import { Injectable } from '@angular/core';
import { CanActivate, Router, ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router';
import { AuthService } from './auth.service';
@Injectable({
  providedIn: 'root'
})
export class AuthGuard implements CanActivate {
  constructor(private authService: AuthService, private router: Router) {}
  canActivate(
    next: ActivatedRouteSnapshot,
    state: RouterStateSnapshot): boolean {
    if (this.authService.isLoggedIn()) {
      return true;
    } else {
      this.router.navigate(['/login']);
      return false;
    }
  }
}

Then, apply the guard to a route:
// app-routing.module.ts
import { AuthGuard } from './auth.guard';
const routes: Routes = [
  { path: 'secure', component: SecureComponent, canActivate: [AuthGuard] }
];

3. Nested Routes
Nested routes, or child routes, help in organizing complex structures where a component has its own sub-routes. It is typically used in dashboard layouts where different sections have their own sub-navigation.

Example
// app-routing.module.ts
const routes: Routes = [
  {
    path: 'dashboard',
    component: DashboardComponent,
    children: [
      { path: 'reports', component: ReportsComponent },
      { path: 'analytics', component: AnalyticsComponent }
    ]
  }
];

In this configuration, navigating to /dashboard/reports and /dashboard/analytics will render ReportsComponent and AnalyticsComponent within the DashboardComponent.

Summary
Advanced routing mechanisms in Angular provide powerful tools for optimizing app performance and enhancing security. By implementing lazy loading, you can decrease initial load times. Route guards enforce security protocols by controlling access to routes. Nested routes allow for a more organized application structure, catering to complex user interfaces. Together, these features enable developers to build robust, efficient, and secure applications.

Sanitization in Angular is an essential component of web development that guards against Cross-Site Scripting (XSS) assaults, ensuring the security of the application. Angular comes with built-in capabilities to sanitize data before it's rendered in the application, shielding it from malicious scripts and safeguarding users.

Recognizing XSS and the Sanitization Need
When a hacker inserts malicious scripts into content from an unreliable source, it's known as an XSS assault. These scripts have the ability to run in the user's browser and may steal information or carry out unauthorized tasks. Angular sanitizes inputs prior to binding them to the DOM in order to reduce these dangers. The integrated sanitization feature of Angular verifies that user data is free of dangerous information.

How Angular Handles Sanitization?
Angular sanitizes data automatically in templates for certain contexts.

• HTML: When binding data to HTML, Angular sanitizes it to prevent the injection of malicious HTML.
• Styles: Angular ensures that style bindings are safe.
• URLs: URL bindings are sanitized to avoid malicious links.
• Resource URLs: When loading resources, Angular ensures URLs are safe.

Using Angular's DomSanitizer
For cases where you need to allow specific trusted content, Angular provides the DomSanitizer service. This service allows you to mark content as safe explicitly.

Example. Using DomSanitizer
Let's create an example where we use DomSanitizer to handle potentially unsafe HTML content safely.

Step 1. Set Up the Angular Project
Create a new Angular project if you don't have one already.

Step 2. Create a Component
Generate a new component for our example.

Step 3. Implement Sanitization in the Component
Modify the safe-content.component.ts to use DomSanitizer.
import { Component } from '@angular/core';
import { DomSanitizer, SafeHtml } from '@angular/platform-browser';

@Component({
  selector: 'app-safe-content',
  templateUrl: './safe-content.component.html',
  styleUrls: ['./safe-content.component.css']
})
export class SafeContentComponent {
  public trustedHtml: SafeHtml;

  constructor(private sanitizer: DomSanitizer) {
    const potentiallyUnsafeHtml = `<div style="color: red;">This is safe content</div>`;
    this.trustedHtml = this.sanitizer.bypassSecurityTrustHtml(potentiallyUnsafeHtml);
  }
}

In this example, we use bypassSecurityTrustHtml to mark the HTML content as safe explicitly.

Step 4. Display the Content in the Template
Modify safe-content.component.html to display the sanitized HTML content.
<div [innerHtml]="trustedHtml"></div>

Step 5. Use the Component in Your App
Include the SafeContentComponent in your app.component.html
<app-safe-content></app-safe-content>

Step 6. Run the Application
Run your Angular application to see the sanitized content in action.

Conclusion
Web security requires sanitization, and Angular offers powerful tools for managing it. Through the use of DomSanitizer and Angular's automated sanitization, developers can guarantee that their apps are safe from cross-site scripting (XSS) threats while maintaining flexibility in content rendering. Building dependable and safe online apps requires an understanding of and adherence to Angular sanitization procedures.

You may handle user-generated content in your Angular applications safely by following the instructions in this article. This will guarantee that your application is secure and that the data of your users is safeguarded.

There are multiple processes involved in creating a comprehensive AngularJS to-do list application. I'll walk you through every step of the process here, including adding, modifying, and removing jobs along with the relevant warnings and duplicate value checking.

A List of Tasks in AngularJS
Install the AngularJS application in step 1.

Make the index.html HTML file
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>AngularJS To-Do List</title>
    <link rel="stylesheet" href="styles.css">
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.8.2/angular.min.js"></script>
    <script src="app.js"></script>
</head>
<body ng-app="todoApp" ng-controller="todoController">
    <div class="container">
        <h1>To-Do List</h1>
        <div class="input-group">
            <input type="text" ng-model="newTask" placeholder="Add a new task" class="form-control">
            <button ng-click="addTask()" class="btn btn-primary">Add Task</button>
        </div>
        <div ng-if="alertMessage" class="alert" ng-class="{'alert-success': alertType=='success', 'alert-danger': alertType=='danger'}">
            {{ alertMessage }}
        </div>
        <ul class="list-group">
            <li ng-repeat="task in tasks" class="list-group-item">
                <span ng-if="!task.editing">{{ task.name }}</span>
                <input type="text" ng-if="task.editing" ng-model="task.name" class="form-control">
                <button ng-if="!task.editing" ng-click="editTask(task)" class="btn btn-warning btn-sm">Edit</button>
                <button ng-if="task.editing" ng-click="saveTask(task)" class="btn btn-success btn-sm">Save</button>
                <button ng-click="deleteTask(task)" class="btn btn-danger btn-sm">Delete</button>
            </li>
        </ul>
    </div>
</body>
</html>

Create the AngularJS file (app.js)
var app = angular.module('todoApp', []);
app.controller('todoController', function($scope) {
    $scope.tasks = [];
    $scope.alertMessage = '';
    $scope.alertType = '';
    $scope.addTask = function() {
        if (!$scope.newTask) {
            $scope.showAlert('Task cannot be empty', 'danger');
            return;
        }
        if ($scope.tasks.some(task => task.name === $scope.newTask)) {
            $scope.showAlert('Task already exists', 'danger');
            return;
        }
        $scope.tasks.push({ name: $scope.newTask, editing: false });
        $scope.newTask = '';
        $scope.showAlert('Task added successfully', 'success');
    };
    $scope.editTask = function(task) {
        task.editing = true;
    };
    $scope.saveTask = function(task) {
        if (!$scope.tasks.some(t => t !== task && t.name === task.name)) {
            task.editing = false;
            $scope.showAlert('Task edited successfully', 'success');
        } else {
            $scope.showAlert('Duplicate task name', 'danger');
        }
    };
    $scope.deleteTask = function(task) {
        var index = $scope.tasks.indexOf(task);
        if (index > -1) {
            $scope.tasks.splice(index, 1);
            $scope.showAlert('Task deleted successfully', 'success');
        }
    };
    $scope.showAlert = function(message, type) {
        $scope.alertMessage = message;
        $scope.alertType = type;
        setTimeout(function() {
            $scope.$apply(function() {
                $scope.alertMessage = '';
            });
        }, 3000);
    };
});

Create a CSS file (styles.css) for styling
body {
    font-family: Arial, sans-serif;
    margin: 20px;
}
.container {
    max-width: 600px;
    margin: auto;
}
.input-group {
    display: flex;
    margin-bottom: 20px;
}
.form-control {
    flex: 1;
    padding: 10px;
    font-size: 16px;
}
.btn {
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
}
.list-group {
    list-style-type: none;
    padding: 0;
}
.list-group-item {
    display: flex;
    justify-content: space-between;
    padding: 10px;
    background-color: #f9f9f9;
    margin-bottom: 5px;
    border: 1px solid #ddd;
}
.alert {
    padding: 10px;
    margin-bottom: 20px;
}
.alert-success {
    background-color: #d4edda;
    border-color: #c3e6cb;
    color: #155724;
}
.alert-danger {
    background-color: #f8d7da;
    border-color: #f5c6cb;
    color: #721c24;
}

Explanation of the Code
HTML Structure

• The HTML file sets up the structure of the To-Do list application.
• It includes an input field for new tasks, a button to add tasks, and a list to display tasks.
• Each task can be edited or deleted.

AngularJS Controller (app.js)

• The todoController manages the tasks array and handles adding, editing, and deleting tasks.
• The addTask function checks for duplicate tasks and alerts the user if a task already exists.
• The editTask function enables editing mode for a task.
• The saveTask function saves the edited task and checks for duplicate names.
• The deleteTask function removes a task from the list.
• The showAlert function displays an alert message for 3 seconds.

Styling (styles.css)

• The CSS file styles the To-Do list application, including the input field, buttons, list items, and alert messages.

By following these steps, you can create a fully functional To-Do list application in AngularJS with features like adding, editing, deleting tasks, and handling duplicate tasks with appropriate alerts.