Angular Domain Specific Language (DSL) Syntax Quiz

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Questions and Answers

What is Angular primarily used for?

Creating server-side applications

Game development

Data analysis

Building web, mobile, and desktop applications (correct)

How does Angular structure an application?

As a collection of random elements

As a series of nested functions

As a single monolithic file

As a tree of individual components (correct)

What do directives do in Angular?

Change the styling of the entire application

Modify the application's core functionality

Add behavior to an existing DOM element or component instance (correct)

Create new components from scratch

Where can you define an Angular component's template?

Inline using the template property or in a separate HTML file (A) Signup and view all the answers

What is the purpose of modules in Angular?

To create logical boundaries in the application (D) Signup and view all the answers

Which of the following is NOT a feature of Angular?

Server-side rendering (A) Signup and view all the answers

What is the purpose of ngOnit in Angular?

To indicate that Angular is done creating the component (A) Signup and view all the answers

Which method is used for creating a new instance by Angular?

Constructor (B) Signup and view all the answers

What does the NullInjector do in Angular?

Throws an error if dependencies are not found (A) Signup and view all the answers

When should the constructor be used in Angular?

To initialize class members (C) Signup and view all the answers

What does a service provide in Angular?

Common functionality to various modules (A) Signup and view all the answers

Where is the platform injector created in an Angular application?

platform browser dynamic function inside main.ts file (B) Signup and view all the answers

What does Dependency Injector do in Angular?

Analyses constructor parameters and resolves dependencies. (C) Signup and view all the answers

What is the Angular module that is commonly known as AppModule?

AppModule (C) Signup and view all the answers

Which package provides the HttpClient in Angular?

@angular/common/http (D) Signup and view all the answers

What does HttpClient.get() method return in Angular?

Observable of typed HttpResponse (A) Signup and view all the answers

How can you handle errors returned by HttpClient in an Angular component?

Adding a second callback to subscribe() method (A) Signup and view all the answers

What is the library used for composing asynchronous and callback-based code in Angular?

RxJS (A) Signup and view all the answers

When does an Observable instance begin publishing values?

Only when someone subscribes to it (D) Signup and view all the answers

What interface is used for receiving observable notifications in Angular?

@observer/Observer (D) Signup and view all the answers

What is the practice of broadcasting to multiple subscribers in a single execution called?

Multi-casting (B) Signup and view all the answers

What are Observables used for in Angular?

Composing asynchronous code (D) Signup and view all the answers

Why should you import observables and operators when using HttpClient in Angular?

To process asynchronous responses (D) Signup and view all the answers

What does the safe navigation operator (?) in Angular help guard against?

Null and undefined values in property paths (D) Signup and view all the answers

How does the safe navigation operator handle null values in Angular?

It returns the null value (B) Signup and view all the answers

Which Angular compiler requires changes in the angular.json configuration file?

AOT compiler (D) Signup and view all the answers

What property is added to the compiler config for the JIT compiler to specify warning level?

'MissingTranslationStrategy' property (A) Signup and view all the answers

In Angular, when does the framework stop evaluating an expression when using the safe navigation operator?

When it finds a null value (C) Signup and view all the answers

Is the @Injectable() decorator mandatory for every service class in Angular?

No, it is not needed for service classes (D) Signup and view all the answers

What determines the type of compilation (JIT or AOT) when running ng build or ng serve commands?

The value of the aot property in angular.json (A) Signup and view all the answers

Which types of functions can't be used to assign values to decorator properties?

Arrow functions or lambda functions (C) Signup and view all the answers

What is the purpose of using macros in Angular applications?

To simplify expression evaluation in metadata (A) Signup and view all the answers

How can you enable binding expression validation explicitly in an Angular project?

Add fullTemplateTypeCheck compiler option in angularCompilerOptions (B) Signup and view all the answers

What does Angular's state() function do?

Defines different states to call at the end of each transition (A) Signup and view all the answers

What does the style() function do in Angular animations?

Defines a set of styles to associate with a given state name (A) Signup and view all the answers

How does Angular support configuration inheritance?

Through extends in tsconfig.json (C) Signup and view all the answers

What component option enables error messages on type errors in template binding expressions?

'fullTemplateTypeCheck' in 'angularCompilerOptions' (D) Signup and view all the answers

'Folding' in Angular refers to:

Evaluating an expression during collection and recording the result (D) Signup and view all the answers

'angularCompilerOptions' are specified as members of which file in an Angular project?

'tsconfig.json' (C) Signup and view all the answers

What does the AsyncPipe do in Angular?

Subscribes to an observable or promise and returns the latest value (C) Signup and view all the answers

Which property binding feature in Angular helps prevent XSS vulnerabilities?

Interpolation using double curly braces (A) Signup and view all the answers

What syntax is used for a template expression in Angular?

{{expression}} (B) Signup and view all the answers

How can you define a component's template location in Angular?

Inline using the template property or in a separate HTML file with templateUrl (B) Signup and view all the answers

What is the purpose of a pipe in Angular?

Transforms data input into a desired output using a simple function (B) Signup and view all the answers

When should you use inline templates versus external template files in Angular?

Use inline templates for small code portions and external templates for larger views (D) Signup and view all the answers

What is the correct syntax for a template statement in Angular?

(event)='statement' (D) Signup and view all the answers

How does Angular handle injected providers?

Determines where to declare providers based on specific rules (A) Signup and view all the answers

What distinguishes a pipe from other Angular features?

'Transforms data input into a desired output by using template expressions' (D) Signup and view all the answers

How does Angular recognize and handle XSS vulnerabilities related to innerHtml property binding?

'Automatically sanitizes input to prevent script injections and XSS attacks' (D) Signup and view all the answers

What is the purpose of the RouterOutlet directive in Angular?

To act as a placeholder for displaying components (D) Signup and view all the answers

How can you create and apply an attribute directive in Angular?

By following specific steps in order (A) Signup and view all the answers

What does ActivatedRoute provide information about in Angular?

Activated routes and resolved data (D) Signup and view all the answers

In Angular routing, what is the purpose of RouterLinkActive?

To toggle CSS classes for active RouterLink bindings (C) Signup and view all the answers

What is the feature of Ahead-of-Time (AOT) compilation in Angular?

It compiles your app at build time by default (D) Signup and view all the answers

How can you access the current RouterState in an Angular application?

By using the Router service and routerState property (D) Signup and view all the answers

What must be configured with a list of route definitions in Angular routing?

@angular/router library (C) Signup and view all the answers

What happens if a URL doesn't match any predefined routes in Angular routing?

The app will throw an error and crash (A) Signup and view all the answers

'NgElement' and 'WithProperties' types are exported from which Angular module?

@angular/elements (B) Signup and view all the answers

What is the purpose of Http Interceptors in Angular?

To inspect and transform HTTP requests (C) Signup and view all the answers

How is a Subject in RxJS different from a plain Observable?

Subjects can multicast to multiple Observers while Observables can't (B) Signup and view all the answers

Which Angular tool allows for the bypassing of the Angular CLI builder?

Bazel (B) Signup and view all the answers

What is the purpose of defining custom unique ids for text messages?

To ensure proper translation extraction (D) Signup and view all the answers

Which platform is the most common context for Angular applications?

Web browsers (C) Signup and view all the answers

How can you report missing translations in Angular?

By displaying a warning message in the console or shell (C) Signup and view all the answers

What is the key role of a Domain Specific Language (DSL) in Angular?

To simplify syntax for writing Angular-specific code (A) Signup and view all the answers

What differentiates an RxJS Subject from an Observable?

Observables can multicast values to many Observers while Subjects can't (D) Signup and view all the answers

How does the Angular injector handle dependencies?

By using a token-provider map to reference dependencies (C) Signup and view all the answers

What is the primary role of Bazel in Angular development?

To allow bypassing of the Angular CLI builder (B) Signup and view all the answers

What does the animation transition function in Angular accept as arguments?

An expression and an animate() function (B) Signup and view all the answers

How can you add enabling Ivy in an existing Angular project?

Use the Ivy flag with ng new command (C) Signup and view all the answers

What is one feature you can expect with Ivy preview in Angular?

Improved AOT compilation speed (D) Signup and view all the answers

When using web workers in Angular, where can you add a web worker?

Anywhere in your application (C) Signup and view all the answers

What is the purpose of an App Shell in Angular applications?

To optimize server-side rendering (B) Signup and view all the answers

What type of decorators come under class decorators in Angular?

@Directive and @Component decorators (B) Signup and view all the answers

What is a DI token in Angular associated with?

A dependency provider in dependency injection system (A) Signup and view all the answers

What is the primary purpose of Dependency Injection in Angular?

To provide dependencies to a component at runtime (B) Signup and view all the answers

Which type of files do completion and diagnostic services work for in Angular?

.ts files only (B) Signup and view all the answers

What does an App Shell help achieve in Angular applications?

Quick initial rendering without JavaScript initialization (C) Signup and view all the answers

What are the benefits of using Ivy preview in Angular?

Faster AOT compilation with recommended configuration options (B) Signup and view all the answers

Study Notes

Introduction to Angular

Angular is a TypeScript-based open-source front-end platform for building web, mobile, and desktop applications.
It offers declarative templates, dependency injection, and end-to-end tooling for easy application development.

Angular Application Structure

An Angular application is divided into separate modules to separate the functionality.
NgModule is a logical boundary in the application, and the application is divided into separate modules.
The NgModule decorator has five important options.

Components and Templates

A template is an HTML view that displays data by binding controls to properties of an Angular component.
Templates can be defined inline or in a separate HTML file.
The @Component decorator is used to link to a separate HTML file.

Lifecycle of Angular Application

The Angular application goes through a lifecycle, which includes initialization and destruction.
The lifecycle methods are used to perform initialization and cleanup tasks.
The constructor is a default method of the class that is executed when the class is instantiated.
ngOnInit is a lifecycle hook that is called by Angular to indicate that Angular is done creating the component.

Dependency Injection

Angular uses a dependency injector to resolve dependencies between components.
The dependency injector is used to provide services to components.
A service is a class that provides a common functionality to various components.
Services allow for greater separation of concerns and better modularity.

Data Binding

Two-way data binding allows data to flow both ways, from the component to the template and from the template to the component.
The [(ngModel)] syntax is used for two-way data binding.
Event binding is used to bind events to component methods.
Property binding is used to bind properties to component properties.
Interpolation is used to add the value of a property to the template.

Pipes

Pipes are simple functions that use template expressions to accept data as input and transform it into a desired output.
Pipes can be chained together to perform complex transformations.
Pipes can accept optional parameters to fine-tune their output.

HTTP and Observables

The HttpClient is used to make HTTP requests to the server.
The HttpClient returns an Observable of typed HttpResponse.
Observables are used to handle asynchronous data.
Observables can be subscribed to receive notifications.
The RxJS library is used to work with Observables.

Angular Elements

Angular Elements are a feature of Angular that allows you to use Angular components as custom elements.
The Angular Elements are packaged as custom elements.
The browser support of Angular Elements is the same as custom elements support.

Routing

The Angular Router is used to navigate between routes.
The RouterOutlet is a directive that marks the spot in the template where the router should display the components.
The RouterLink is a directive that gives the router control over anchor tags.
The RouterLinkActive is a directive that toggles CSS classes for active RouterLink bindings.
The RouterState is a tree of activated routes.
The ActivatedRoute contains information about a route associated with a component.
The RouterModule is used to configure the router with routes.

Compilation

Ahead-of-Time (AOT) is a type of compilation that compiles your app at build time.
AOT is the default starting in Angular 9.### Angular Compilation
Angular compilation depends on the aot property in the build configuration specified in angular.json.
By default, aot is set to true.
AOT (Ahead-of-Time) compilation benefits:
- Faster rendering
- Smaller bundles
- Better performance

AOT Compiler

The AOT compiler supports macros in the form of functions or static methods that return an expression in a single return statement.
Macros can be used inside metadata as an expression.
The compiler treats the macro expression as if it was written directly.
Example of a macro function:
- let macroFunction = () => { return 'some value'; }

Errors in Metadata

Errors encountered in metadata:
- Unable to refer to selector references because they are not exported.
- Unable to fold some expressions, such as spread operators on arrays, objects created using new keywords, and function calls.
The compiler can only resolve references to exported symbols in the metadata.

Angular Compiler Options

Angular compiler options are specified as members of the angularCompilerOptions object in the tsconfig.json file.
These options are specified adjacent to TypeScript compiler options.
Example: fullTemplateTypeCheck compiler option to enable binding expression validation.

Dependencies

The dependencies section of package.json in an Angular application can be divided into:
- Dependencies
- DevDependencies
- PeerDependencies
Installing Angular Language Service in a project using the npm command: npm install @angular/language-service

Navigation features in Angular:
- Hovering over a component, directive, or module and clicking F12 to go directly to its definition.
- Error checking and warnings for mistakes in code.
- Autocompletion for contextual possibilities and hints as you type.

Web Workers

Adding web workers to an Angular project:
- Using the ng generate web-worker command to create a web worker file.
- Refactoring initial scaffolding web worker code for sending messages to and from.
Important things to remember when using Web Workers in Angular projects:
- Web workers run in a separate context from the main thread.
- Web workers communicate with the main thread using messages.

App Shell

App shell is a way to render a portion of an application via a route at build time.
Benefits of using app shell:
- Faster rendering of the initial page load.
- The browser can render static HTML and CSS without the need to initialize JavaScript.
Achieving app shell using Angular CLI, which generates an app shell for running server-side of the app.

Case Types

Angular follows capitalization conventions to distinguish the names of various types:
- PascalCase (UpperCamelCase)
- camelCase (lowerCamelCase)
- UPPERCASE
- lowercase
- kebab-case (lower-kebab-case)

Decorators

Class decorators:
- Immediately before a class definition.
- Declares the class to be of a given type.
- Provides metadata suitable to the type.
Class field decorators:
- Immediately before a field in a class definition.
- Defines the type of that field.
Examples: @Input and @Output

DI Tokens

DI token is a lookup token associated with a dependency provider in the dependency injection system.
The injector maintains an internal token-provider map that it references when asked for a dependency.
Example of DI token usage:
- Providing a token for a service:
  - let token = new InjectionToken('myServiceToken');
  - @Inject(token) private myService: MyService

DSL

Angular has its own Domain Specific Language (DSL) which allows writing Angular-specific HTML-like syntax on top of normal HTML.
The DSL is defined in NgModules such as animations, forms, and routing and navigation.
Angular DSL has its own compiler that compiles this syntax to HTML that the browser can understand.

Subjects

RxJS Subject is a special type of Observable that allows values to be multicasted to many Observers.
Subjects maintain a registry of many listeners.
While plain Observables are unicast, Subjects are multicast.

Bazel

Bazel is a tool for building and testing software.
Key advantages of using Bazel:
- Faster builds
- Better performance
- Improved scalability
Running Bazel directly using the Bazel CLI:
- Installing the Bazel CLI globally using the @bazel/bazel npm package.
- Using common commands such as bazel build, bazel run, and bazel test.

Platforms

A platform is the context in which an Angular application runs.
The most common platform for Angular applications is a web browser.
Angular can be used as a platform-independent framework in different environments, such as:
- Mobile devices
- Web servers
- Desktop applications

View Child

Using the @ViewChild directive to access elements in the view directly.
Example: accessing an input element with a reference:
- ``
- @ViewChild('myInput') myInput: ElementRef

Router

Subscribing to the router to detect changes:
- this.router.events.subscribe(event => { ... });

Http Interceptors

Http Interceptors are part of @angular/common/http.
They inspect and transform HTTP requests from the application to the server and vice versa.
Interceptors can perform a variety of implicit tasks, such as authentication and logging.
Example of an Http Interceptor interface:
- intercept(request: HttpRequest, next: HttpHandler): Observable>
Using interceptors by declaring a service class that implements the intercept() method of the HttpInterceptor interface.

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Test your knowledge on the syntax of Angular's Domain Specific Language (DSL) used for writing Angular-specific html-like syntax. Learn about how Angular's injector maintains an internal token-provider map and references it when asked for a dependency.