Tech Point Fundamentals

Saturday, February 17, 2024

Angular Interview Questions and Answers - Part 22

angular-interview ,
Angular Interview Questions and Answers - Part 22

Angular Interview Questions and Answers - Part 22

Angular-Interview-Questions-And-Answers

Angular is a popular single-page application design framework and development platform. It is a robust open-source JavaScript framework that is widely used for front-end application development. Nowadays Angular is very famous as a frontend technology so it is important from the interview point as well. 

Introduction


This is the Angular Interview Questions and Answers series. Here we will see 200+ Most Frequently Asked Angular Interview Questions. This is the 22nd part of the Angular Interview Questions and Answer series.

I will highly recommend that you visit the following parts before continuing to this part:



Please do visit our YouTube Channel here to watch Interview Questions & Answers and important technology videos.

In this part we will discuss the following Important Angular Interview Questions:

Q246. How do you get the current route in Angular?
Q247. What is the safe navigation operator in Angular? 
Q248. What is the non-null assertion operator in Angular? How it is different from a safe navigation operator?
Q249. What does mean by relative path in Angular? How can you specify a relative route in Angular?
Q250. What is the child route in angular? How it is different from Nesting routes? 
Q251. What is the page title? How can you set the page title in Angular?
Q252. What is the Link Parameters Array in Angular?
Q253. What are the default LocationStrategy and URL styles supported by Angular?
Q254. What is the purpose of <base href> tag in Angular?
Q255. What do you understand by the RouterState?

Angular Interview Questions and Answers: Part 22


Q246. How do you get the current route in Angular?

There are different ways to get the current route in angular. You can get the URL property in both ActivatedRoute and Router service.

In Angular, there is a URL property of the router package to get the current route. In Angular, you can get the current route by injecting the ActivatedRoute service into your component and subscribing to its URL property. However, you can also get the same by using the Router service as well.

When the route changes, the URL property emits a new value, which can be accessed in the subscription callback. Import the Router from @angular/router and then Inject the router inside the constructor.

import { ActivatedRoute, Router} from '@angular/router';

export class ActivatedRouteDemoComponent {
  constructor(private route: ActivatedRoute, private router: Router) {
       console.log('Current URL: ' + this.router.url);    
  }

  ngOnInit() {
    this.route.paramMap.subscribe(url => {
      console.log('Current URL: ' + url );
    });
}

You can get the current route by accessing the router.url property. But If you are navigating the routes with Hash location strategy, the router.url will always return “/”. So it’s advisable to listen to the NavigationEnd event of the router to get the current route URL in Angular.

import { Router, NavigationEnd  } from '@angular/router';

constructor(private router: Router) {       
    this.router.events.subscribe((event) => {      
    event instanceof NavigationEnd ? console.log('Currunt URL: ' + event.url): null    
  })
}

Q247. What is the safe navigation operator in Angular?

In Angular safe navigation operator (?), guards against null and undefined values in property paths. The safe navigation operator is represented by the ?. symbol and is used to access the properties of an object without causing an error if the object is null or undefined. 

With the safe navigation operator, ?, the Angular framework stops evaluating the expression when it hits the first null value and renders the view without any errors.

The safe navigation operator in Angular is a feature that allows you to guard against null and undefined values in property paths when you are not aware of whether a path exists or not. It is also known as the Elvis Operator.

If there is no safe navigation operator and nullItem is null, JavaScript and Angular would throw a null reference error and break the rendering process of Angular: TypeError: Cannot read property 'name' of null.

<p>The user name is: {{user?.name}}</p>

Here, it protects against a view render failure if the user is null. If the user object is null, the view still renders but the displayed value is blank; you see only "The user name is:" with nothing after it.

Sometimes, however, null values in the property path may be OK under certain circumstances, especially when the value starts out null but the data arrives eventually.  The safe navigation operator works perfectly with long property paths such as a?.b?.c?.d.

Q248. What is the non-null assertion operator in Angular? How it is different from a safe navigation operator?

The non-null assertion operator (!) in Angular is a TypeScript feature that allows developers to assert that a value is not null or undefined. It is represented by the exclamation mark (!) and is used to suppress the “Object is possibly "null" or "undefined" error that occurs when TypeScript cannot determine if a value is null or undefined.

It is important to note that the non-null assertion operator should only be used when you are certain that a value is not null or undefined. If there is any doubt, it is better to use optional chaining or null coalescing instead.

    <p>The item's color is: {{item.color!.toUpperCase()}}</p>

When the Angular compiler turns your template into TypeScript code, it prevents TypeScript from reporting that item.color might be null or undefined.

As of Typescript 2.0, you can enforce strict null checking with the --strictNullChecks flag. TypeScript then ensures that no variable is unintentionally null or undefined. In this mode, typed variables disallow null and undefined by default. The type checker throws an error if you leave a variable unassigned or try to assign null or undefined to a variable whose type disallows null and undefined.

The type checker also throws an error if it can't determine whether a variable will be null or undefined at runtime. You tell the type checker not to throw an error by applying the postfix non-null assertion operator.

Unlike the safe navigation operator, the non-null assertion operator does not guard against null or undefined. Rather, it tells the TypeScript type checker to suspend strict null checks for a specific property expression. The non-null assertion operator, !, is optional with the exception that you must use it when you turn on strict null checks.

Q249. What does mean by relative path in Angular? How can you specify a relative route in Angular?

In Angular, a relative path is a path that is relative to the current URL segment. It is used to define paths that are relative to the current component’s route. Relative paths let you define paths that are relative to the current URL segment. The path: ' ' means to use the initial relative URL (' ').

In Angular, relative paths are used to import modules and components that are located in the same or sibling directory as the current file. Relative paths are specified using the" ./" and "../" syntax. The "./" syntax is used to specify the current directory, while the "../" syntax is used to specify the parent directory.

For example, if you are currently at the URL /products, and you want to navigate to the URL /products/details, you can use a relative path of details to navigate to the details route relative to the current URL segment.

For example, if you have a component located in the same directory as the current file, you can import it using a relative path like this:

import { MyComponent } from './my-component';

If you have a component located in a sibling directory, you can import it using a relative path like this:

import { MyComponent } from '../my-sibling-directory/my-component';

To specify a relative route in Angular, you can use the relativeTo property of the NavigationExtras object. This property specifies the route that the relative path is relative to. In the component class, import NavigationExtras from the @angular/router.

For example, if you want to navigate to the details route relative to the current URL segment, you can use the following code:

import { Router} from '@angular/router';

export class ActivatedRouteDemoComponent {
constructor(private router: Router) {    
}
goToDetails() {
    this.router.navigate(['details'], { relativeTo: this.route });
  }
}

Relative paths can be useful for organizing your application’s code into smaller, more manageable modules and components. However, as your application grows larger, relative paths can become cumbersome and difficult to maintain. In such cases, it may be better to use absolute paths or a module loader like SystemJS.

Q250. What is the child route in angular? How it is different from Nesting routes? 

In Angular, a child route is a route that is nested inside another route. It is used to define routes that are relative to the current component’s route. Child routes are useful when you want to create a hierarchical navigation structure in your application.

As your application grows more complex, you might want to create routes that are relative to a component other than your root component. These types of nested routes are called child routes. This means you're adding a second <router-outlet> to your app because it is in addition to the <router-outlet> in AppComponent.

A child route is like any other route, in that it needs both a path and a component. The one difference is that you place child routes in a children array within the parent route. You can also define multiple child routes inside a parent route.

To define a child route in Angular, you need to specify the parent route and the child route in your routing configuration. The child route is defined as an array of routes inside the parent route.

const routes: Routes = [
  { path: 'parent', component: ParentComponent,
    children: [
      { path: 'child1', component: Child1Component },
      { path: 'child2', component: Child2Component }
  ]
  }
];

In this example, there are two additional child components, child-1, and child-2.

  <h2>Parent Component</h2>
  <nav>
    <ul>
    <li><a routerLink="child-a">Child 1</a></li>
    <li><a routerLink="child-b">Child 2</a></li>
    </ul>
  </nav>
  <router-outlet></router-outlet>

Q251. What is the Page Title? How can you set the page title in Angular?

Each page in your application should have a unique title so that it can be identified in the browser history. The Router sets the document's title using the title property from the Route config.

In Angular, the page title is the text that appears on the browser tab for a particular page. It is an important aspect of web development as it helps users identify the purpose of the page and search engines to index it properly.

const routes: Routes = [
  {
  path: 'product-component',
  title: 'Product',
  component: ProductComponent,
  children: [
    {
    path: 'home-product',  
    title: resolvedChildTitle,
    component: HomeProduct,  
    },
    {
    path: 'service-product',
    title: 'service-product',
    component: ServiceProduct,  
    },
  ],
  },
];
const resolvedChildTitle: ResolveFn<string> = () => Promise.resolve('home-product');

The title property follows the same rules as static route data and dynamic values that implement ResolveFn<>. You can also provide a custom title strategy by extending the TitleStrategy.

To set the page title dynamically in Angular, you can use the Title service provided by @angular/platform-browser. Here are the steps to set the page title:

  • Import the Title service in your component
  • Inject the Title service in your component’s constructor
  • Use the setTitle() method of the Title service to set the page title

You can set the page title dynamically by passing a string variable to the setTitle() method.

import { Title } from '@angular/platform-browser';

constructor(private titleService: Title) { }

let pageTitle = 'Tech Point Fundamentals';
this.titleService.setTitle(pageTitle);

Q252. What is the Link Parameters Array in Angular?

In Angular, a link parameters array is an array of values that are used to construct a URL for a particular route. It is used to pass data between components and to navigate to different routes in your application. A link parameters array holds the following ingredients for router navigation:

  • The path of the route to the destination component
  • Required and optional route parameters that go into the route URL

To create a link parameters array in Angular, you can use the routerLink directive in your HTML template. The routerLink directive accepts an array of values that represent the route you want to navigate to. You can bind the RouterLink directive to such an array like this:

  <a [routerLink]="['/products', productId]">View Product</a>

In this example, the routerLink directive is used to create a link to the /products route with a parameter of productId. When the user clicks on the link, the productId value is passed to the product component, which can then be used to display the appropriate product details.

You can also pass additional parameters to a route by including them in the link parameters array.

 <a [routerLink]="['/products', productId, { color: 'red', size: 'large' }]">View Product</a>

In this example, the color and size parameters are passed to the product component along with the productId parameter.

Q253. What are the default LocationStrategy and URL styles supported by Angular?

When the router navigates to a new component view, it updates the browser's location and history with a URL for that view. Modern HTML5 browsers support history.pushState, a technique that changes a browser's location and history without triggering a server page request. The router can compose a "natural" URL that is indistinguishable from one that would otherwise require a page load.

For example in the "HTML5 pushState" style: localhost:3002/product-details

However, Older browsers send page requests to the server when the location URL changes unless the change occurs after a "#" (called the "hash"). Routers can take advantage of this exception by composing in-application route URLs with hashes.

localhost:3002/src/#/product-details

LocationStrategy Providers in Angular:

The Angular router supports both location strategy styles with two LocationStrategy providers:

PathLocationStrategy: The default "HTML5 pushState" style.
HashLocationStrategy: The "hash URL" style.

In Angular, the default LocationStrategy is PathLocationStrategy. This strategy uses the HTML5 history API to manipulate the browser’s URL and history. It allows you to use normal-looking URLs without the hash symbol (#).

The other LocationStrategy supported by Angular is HashLocationStrategy. This strategy uses the hash symbol (#) in the URL to manipulate the browser’s history. It is useful for older browsers that do not support the HTML5 history API. Use HashLocationStrategy by providing the useHash: true in an object as the second argument of the RouterModule.forRoot() in the AppModule.

@NgModule({
  imports: [
  BrowserModule,
  FormsModule,
  RouterModule.forRoot(routes, { useHash: true })  
  ]
})

To use PathLocationStrategy, you need to add a <base href> element to your index.html file. This element specifies the base URL for all relative URLs in your application.

The RouterModule.forRoot() function sets the LocationStrategy to the PathLocationStrategy, which makes it the default strategy. You also have the option of switching to the HashLocationStrategy with an override during the bootstrapping process.

You must choose a routing strategy early in the development of your project because once the application is in production, visitors to your site use and depend on application URL references. Almost all Angular projects should use the default HTML5 style. It produces URLs that are easier for users to understand and it preserves the option to do server-side rendering.

Q254. What is the purpose of <base href> tag in Angular?

In Angular, the <base href> tag is used to specify the base URL for all relative URLs in your application. It is an important element for generating correct routes, especially when you are deploying your project in a subfolder.

The href attribute is used to specify the base URL for all relative URLs on a page. During navigation, the base href tag is used by the Angular router as a base path to the component, template, and module files.

The base href element has the Angular router to compose the navigation URLs. It tells the browser where actually the script files will execute and it helps the router to compose a navigation URL. A relative base URL helps in indexing better on the website server or on the working local website copy. 

By default, the value is set to "/" i.e root which means the scripts are in root the directory. The base href is mentioned in the index.html file within the <head></head> tags. This guide works with a CLI-generated Angular application. 

If you are working manually, make sure that you have <base href="/"> in the <head> of your index.html file. However, if your application is deployed at https://techpointfunda.com/prod/, you would set the base href tag to <base href="/prod/">. This ensures that all relative URLs in your application are resolved relative to the /prod/ path.

The routing application should add an element to the index.html as the first child in the tag to indicate how to compose navigation URLs. If the app folder is the application root then you can set the href value as below:

<head>
  <meta charset="utf-8">
  <title>TechPoint</title>
  <base href="/">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" type="image/x-icon" href="favicon.ico">
</head>

When you use the Angular router to navigate between different views and components in your application, it uses the base href tag to compose the navigation URLs. Without that tag, the browser might not be able to load resources (images, CSS, scripts) when "deep linking" into the application. 

If you do not set the base href tag, the Angular router will use the current URL as the base URL for all relative URLs in your application. This can cause issues if your application is deployed in a subdirectory or if you are using a server-side rendering solution.

You must add a <base href> element to the application's index.html for pushState routing to work. The browser uses the <base href> value to prefix relative URLs when referencing CSS files, scripts, and images.

Q255. What do you understand by the RouterState?

In Angular, the RouterState is a tree of activated routes that represents the state of the router as it keeps changing over time when users navigate from page to page.  Every node in this tree knows about the "consumed" URL segments, the extracted parameters, and the resolved data. It is an immutable data structure that contains the current state of the router, including the current URL, the current route, and any route parameters or query parameters.

The RouterState is created by the Angular router and is updated every time the user navigates to a new route. It is used by the router to determine which components to display on the screen and how to arrange them.

You can access the RouterState in your Angular application by injecting the ActivatedRoute service into your component. The ActivatedRoute service provides access to the current route’s state, including the RouterState.

The router state in Angular represents the current state of the Angular router. It contains information about the current route, including the URL, route parameters, query parameters, and other related data. The router state can be accessed and manipulated using the Angular Router service. It provides a way to programmatically navigate, retrieve information about the current route, and handle route changes in Angular applications.

You can access the current routerState from anywhere in the application using the Router service and the routerState property.

import { RouterState } from '@angular/router';

@Component({templateUrl:'index.html'})
  class MyComponent {
    constructor(router: Router) {
    const state: RouterState = router.routerState;
    const root: ActivatedRoute = state.root;
    const child = root.firstChild;
    const id: Observable<string> = child.params.map(p => p.id);
    }
  }





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Saturday, February 10, 2024

Angular Interview Questions and Answers - Part 21

angular-interview ,
Angular Interview Questions and Answers - Part 21

Angular Interview Questions and Answers - Part 21

Angular-Interview-Questions-And-Answers

Angular is a popular single-page application design framework and development platform. It is a robust open-source JavaScript framework that is widely used for front-end application development. Nowadays Angular is very common as frontend technology so it is very common for the interview point as well. 

Introduction


This is the Angular Interview Questions and Answers series. Here we will see 200+ Most Frequently Asked Angular Interview Questions. This is the 21st part of the Angular Interview Questions and Answer series.

I will highly recommend to please do visit the following parts before continuing to this part:



Please do visit our YouTube Channel here to watch Interview Questions & Answers and important technology videos.

In this part we will discuss the following Important Angular Interview Questions:

Q235. What are the wildcard routes in Angular? Why it is important in any application?
Q236. What are URL Redirects in Angular? How can you set up redirects in the Angular?
Q237. What is the pathMatch in Angular? What is the default value of the pathMatch?
Q238. What is the difference between pathMatch and redirectTo in Angular?
Q239. What is AppRoutingModule in Angular? What are the advantages of using a routing module?
Q240. Does routing modules import order matter in Angular?
Q241. What is the use of RouterOutlet in Angular?
Q242. What is the difference between RouterLink vs. RouterLinkActive in Angular?
Q243. Can you skip the Routing Module in Angular? Do we need a Routing Module always?
Q244. What is the use of router.navigate in Angular?
Q245. What is the Activated Route in Angular?

Angular Interview Questions and Answers: Part 21


Q235. What are the wildcard routes in Angular? Why it is important in any application?

In Angular, wildcard routes are used to handle undefined or unknown routes in an application. If the URL doesn't match any predefined routes then it causes the router to throw an error and crash the app. In this case, you can use the wildcard route.  When the router encounters a URL that doesn’t match any defined routes, it can redirect or display a specific component designated for handling such scenarios.

A well-functioning application should gracefully handle when users attempt to navigate to a part of your application that does not exist. To add this functionality to your application, you set up a wildcard route. The Angular router selects this route any time the requested URL doesn't match any router paths.

To set up a wildcard route, you can define a route with a path consisting of two asterisks (**). This route will be selected by the router if the requested URL doesn’t match any of the paths defined in the earlier configuration.

const routes: Routes = [
  { path: 'User', component: UserComponent },
  { path: '**', component: PageNotFoundComponent }
];

The last route with the path of ** is a wildcard route. The two asterisks, **, indicate to Angular that this route's definition is a wildcard route. For the component property, you can define any component in your application.  

The router selects the route with a first-match wins strategy. Because a wildcard route is the least specific route, place it last in the route configuration.

Common choices include an application-specific PageNotFoundComponent, which you can define to display a 404 page to your users; or a redirect to your application's main component. A wildcard route is the last route because it matches any URL. 

Q236. What are URL Redirects in Angular? How can you set up redirects in the Angular?

In Angular, URL redirects are used to navigate the user to a different URL or route within the application. This is useful when you want to redirect the user to a different page after they have completed an action or when you want to redirect them to a different page based on certain conditions.

To redirect the user to a different route within your Angular application, you can use the Router service. This service provides methods for navigating between routes in your application. 

External URL Redirection: 

To redirect the user to a different external URL, you can use the window.location.href property. This property sets or returns the entire URL of the current page, including the protocol, hostname, and query string.

 window.location.href = 'https://www.techpointfunda.com';

Alternatively, you can use the document.location.href as well. The document.location.href is a property that returns the entire URL of the current page. In Angular, you can use window.location.href to redirect to an external URL. To use this, you need to import DOCUMENT from @angular/common.

import { DOCUMENT } from '@angular/common';
constructor(@Inject(DOCUMENT) private document: Document)
{
    this.document.location.href = 'https://www.techpointfunda.com';
}

Internal URL Redirection:

To redirect the user to a different route within your Angular application, you can use the Router service. This service provides methods for navigating between routes in your application.

import { Router } from '@angular/router';
constructor(private router: Router) {
  this.router.navigate(['/home']);
}

Alternatively, to set up a redirect, you can configure a route with the path you want to redirect from, the component you want to redirect to, and a pathMatch value that tells the router how to match the URL.

Use of Internal Redirect:

When the application launches, the initial URL in the browser bar is by default: localhost:4200

That doesn't match any of the hard-coded routes which means the router falls through to the wildcard route and displays the PageNotFoundComponent. 

However, the application needs a default route to a valid page. The application should navigate there as if the user clicked the "Home" link or pasted localhost:4200/home into the address bar.

So you need to add a redirect route that translates the initial relative URL (' ') to the default path (/home) you want. You must add the default route somewhere above the wildcard route. It's just above the wildcard route in the following example.

const routes: Routes = [
  { path: 'User', component: UserComponent },  
  { path: '',   redirectTo: '/home-component', pathMatch: 'full' },
  { path: '**', component: PageNotFoundComponent }
];

A redirect route requires a pathMatch property to tell the router how to match a URL to the path of a route. When pathMatch is set to full, Angular will search for the exact path in the URL in the routes array. This is useful when you want to redirect the user to a specific page or route.

Here notice that this redirect precedes the wildcard route. Here, empty path: ' ' means to use the initial relative URL (' ').

Q237. What is the pathMatch in Angular? What is the default value of the pathMatch?

In Angular, pathMatch is a property that is used to define how Angular matches the requested URL against the configured routes. 

There are two possible values for pathMatch: prefix and full. The default behavior of Angular is to use prefixes for all routes.

Full PathMatch:

When pathMatch is set to full, Angular will search for the exact path in the URL in the routes array. This is useful when you want to redirect the user to a specific page or route.

Technically, pathMatch = 'full' results in a route hit when the remaining, unmatched segments of the URL match ' '. 

For example, if you want to redirect the user to the home page when they visit your website’s root URL, you can use full pathMatch:

{ path: '',   redirectTo: '/home-component', pathMatch: 'full' }

Prefix PathMatch:

The other possible pathMatch value is 'prefix' which tells the router to match the redirect route when the remaining URL begins with the redirect route's prefix path. This is the default in Angular. 

Q238. What is the difference between pathMatch and redirectTo in Angular?

In Angular, pathMatch, and redirectTo are two properties that are used to configure the behavior of the router.

The pathMatch is a property that is used to define how Angular matches the requested URL against the configured routes. There are two possible values for pathMatch: prefix and full. The default behavior of Angular is to use prefix for all routes.

On the other hand, redirectTo is a property that is used to redirect the user to a different route when they visit a specific URL. For example, if you want to redirect the user from login to the dashboard:

 { path: 'login', redirectTo: '/dashboard'}

Q239. What is AppRoutingModule in Angular? What are the advantages of using a routing module?

The routing module, often called the AppRoutingModule, replaces the routing configuration in the root or feature module. AppRoutingModule is a NgModule in Angular that is used to configure the routes of an Angular application. It is generated by the Angular CLI when you create a new application with routing enabled.

The routing module is helpful as your application grows and when the configuration includes specialized guard and resolver functions.

Some developers skip the routing module when the configuration is minimal and merge the routing configuration directly into the companion module (for example, AppModule).

Most applications should implement a routing module for consistency. It keeps the code clean when the configuration becomes complex. It makes testing the feature module easier. Its existence calls attention to the fact that a module is routed. It is where developers expect to find and expand routing configuration.

Advantages of Routing Module:

The primary advantage of using a routing module in Angular is that it helps you manage the navigation and routing of your application in a structured and organized way. By defining your routes in a separate module, you can keep your code modular and easy to maintain. 

You can also use lazy loading to load only the necessary modules and components when they are needed, which can improve the performance of your application.

Another advantage of using a routing module is that it allows you to define guards to protect your routes from unauthorized access. Guards are used to control access to certain routes based on user authentication or other criteria. For example, you can use a guard to prevent unauthenticated users from accessing certain parts of your application.

Q240. Does routing modules import order matter in Angular?

Yes, if you have multiple routing modules and you want to register and use them at the application root level, the order of import in the import array matters. The order of route configuration is important because the router accepts the first route that matches a navigation request path. 

The router selects the route with a first-match wins strategy. Because a wildcard route is the least specific route, place it last in the last route configuration.

 imports: [
    BrowserModule,    
    HttpClientModule,
    UserRoutingModule,
    AppRoutingModule
  ]

Here notice that in the module imports array, the AppRoutingModule is last and comes after the UserRoutingModule. When all routes were in one AppRoutingModule, you put the default and wildcard routes last, after the /user route, so that the router had a chance to match a URL to the /user route before hitting the wildcard route and navigating to "Page not found".

Each routing module augments the route configuration in the order of import. If you listed AppRoutingModule first, the wildcard route would be registered before the user routes. The wildcard route which matches every URL would intercept the attempt to navigate to a user route.

Q241. What is the use of RouterOutlet in Angular?

The router outlet serves as a placeholder where the routed components are rendered. The RouterOutlet is a directive from the router library and it acts as a placeholder that marks the spot in the template where the router should display the components for that outlet. The router outlet is used as a component.

Router Outlet is a directive in Angular that is used to mark where in a template, a matched component should be inserted.  It is available from the @angular/router package and is used by the router to insert a matched component in a template.

The router outlet is used to create multiple views/pages in an application. The app template acts like a shell of your application, and any element you add to the shell will be rendered in each view. Only the part marked by the router outlet will be changed between views.

You can also name the router outlet using the name property. You can have multiple outlets in your Angular template. The unnamed outlet is the primary outlet in your app, and except for the primary outlet, all the other outlets must have a name. You can specify the router outlet where you want to insert the route component using the outlet.

You can add a router outlet to the main application template that exists in the src/app/app.component.html file associated with the root App component.

<nav>
  <ul>
    <li><a routerLink="/home-component" routerLinkActive="active" ariaCurrentWhenActive="page">HOME </a></li>
    <li><a routerLink="/user-component" routerLinkActive="active" ariaCurrentWhenActive="page">USER</a></li>
  </ul>
</nav>
<router-outlet></router-outlet>

Q242. What is the difference between RouterLink vs. RouterLinkActive in Angular?

RouterLink and RouterLinkActive are both directives in Angular that are used to navigate between different views of an application. In summary, RouterLink is used to navigate to a specific route, while RouterLinkActive is used to highlight the active link in the navigation menu.

RouterLink:

RouterLink is a directive that is used to navigate to a specific route when clicked. It is used to bind a clickable HTML element to a route. You can use it to navigate to a specific route by binding it to a string or an array of strings that represent the route path. 

You can also use it to bind to a variable that represents the route path. When the user clicks on the element, the router navigates to the specified route.

<nav>
      <ul>
        <li><a routerLink="/home-component" routerLinkActive="active" ariaCurrentWhenActive="page">HOME </a></li>
        <li><a routerLink="/user-component" routerLinkActive="active" ariaCurrentWhenActive="page">USER</a></li>
      </ul>
 </nav>

RouterLinkActive:

RouterLinkActive is a directive that is used to add a CSS class to an element when the link is active. It is used to highlight the active link in the navigation menu. You can use it to add a CSS class to the element when the link is active. 

The directive adds the class when the link is active and removes it when the link is inactive. You can also use it to add a CSS class to the element when the link is partially active.

RouterLinkActive is a directive that toggles CSS classes for active RouterLink bindings based on the current RouterState. The Router will add CSS classes when this link is active and remove when the link is inactive. 

Q243. Can you skip the Routing Module in Angular? Do we need a Routing Module always?

In angular the Routing Module is a design choice. You can skip the routing Module (AppRoutingModule) when the configuration is simple and merge the routing configuration directly into the companion module (AppModule). However, it is recommended when the configuration is complex and includes specialized guard and resolver services.

The Angular router is an external, optional NgModule called RouterModule. It is not mandatory to use the routing module in Angular, but it is highly recommended to use it for better organization and maintainability of your application.

The routing module provides a way to map URLs to components in your application. It also provides a way to navigate between different views and components in your application.

If you choose not to use the routing module, you will have to manually handle navigation between different components and views in your application. This can be a tedious and error-prone process, especially for larger applications.

Q244. What is the use of router.navigate in Angular?

In Angular, router.navigate() is a method of the Router class that allows you to navigate to a specific route programmatically. It is used to navigate to a specific route by specifying the route path and any required parameters.

Router.navigate specifies a root URL through relative navigation. This function can be used to navigate in Angular. You can also pass additional parameters to the route by specifying them as an object in the second parameter of the router.navigate() method.

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

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.sass']
})
export class HomeComponent {
  constructor(private router: Router) {}
  goToRoute() {
  this.router.navigate(['/home']);
  }
}

In the above example, router.navigate(['/home']) navigates to the route with the path home.

Q245. What is the Activated Route in Angular?

In Angular, the ActivatedRoute is a service that provides access to information about the currently activated route. It is part of the @angular/router module and is used to extract information about the current route, such as route parameters, query parameters, and URL segments.

The ActivatedRoute service is typically injected into a component’s constructor using Angular’s dependency injection system. ActivatedRoute contains the information about a route associated with a component loaded in an outlet. It can also be used to traverse the router state tree. The ActivatedRoute will be injected as a router service to access the information. 

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

@Component({
  selector: 'app-activated-route-demo',
  templateUrl: './activated-route-demo.component.html',
  styleUrls: ['./activated-route-demo.component.sass']
})
export class ActivatedRouteDemoComponent {  
  constructor(private route: ActivatedRoute) {}

  ngOnInit() {
  this.route.paramMap.subscribe(params => {
    console.log('Route Parameters : ' + params ); // Access route parameters here
  });

  this.route.queryParamMap.subscribe(params => {
    console.log('Query Parameters : ' + params ); // Access query parameters here
  });
  }
}




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