What is the purpose of the setValue and patchValue methods in Angular Reactive Forms?
- They both reset the form
- They both set the entire form
- patchValue sets partial values
- setValue sets a specific value
In Angular Reactive Forms, setValue sets the entire form, while patchValue sets partial values. patchValue is commonly used to update specific form controls.
What is the difference between a BehaviorSubject and a ReplaySubject?
- A BehaviorSubject emits all previous values
- A BehaviorSubject emits the last value
- A ReplaySubject emits all previous values
- A ReplaySubject emits the last value
The key difference is that a BehaviorSubject emits only the last value upon subscription, while a ReplaySubject emits all previous values to new subscribers.
In Angular, how can you prevent the default form submission behavior of a page reload?
- Set action="javascript:void(0)"
- Use (click)="preventDefault()"
- Use (ngSubmit)="onSubmit($event)"
- Use (submit)="preventDefault()"
To prevent the default form submission behavior of a page reload in Angular, you should use (ngSubmit)="onSubmit($event)" and handle the form submission in your component.
You are building a large e-commerce application and you want to ensure that certain modules, like the Checkout module, are only loaded when the user navigates to that section. How would you achieve this?
- Dynamic import() in JavaScript to load modules asynchronously
- Lazy loading with Angular Routing
- Using Webpack code splitting during the build process
- Using ngModule imports in Angular module configurations to control module loading
In Angular, you can achieve lazy loading of modules, such as the Checkout module, using Angular Routing. It allows you to load modules on-demand when a specific route is accessed, improving performance by reducing initial load times.
How can you preload data for a route before navigating to it?
- Component resolver
- Lazy loading
- Preloading strategy
- Router pre-fetching
To preload data for a route before navigating to it, you can use a Preloading strategy. A preloading strategy allows you to load data or modules in the background so that they are available when needed.
The _____ testing utility in Angular helps you test code that contains asynchronous operations.
- ComponentFixture
- HttpClientTestingModule
- Karma
- TestBed
The blank should be filled with TestBed. The TestBed utility in Angular helps you set up and configure an environment for testing Angular components, services, and more.
To optimize performance, you can set the _____ property of a component to ChangeDetectionStrategy.OnPush to make Angular check the component only when its input properties change.
- OnCheck
- changeDetectionStrategy
- detectionChangeStrategy
- ngChangeDetection
To optimize performance in Angular, you can set the changeDetection property of a component to ChangeDetectionStrategy.OnPush. This setting makes Angular check the component only when its input properties change, reducing unnecessary checks and improving performance.
Which RxJS operator is best suited for performing side effects in an Observable chain?
- filter
- map
- reduce
- tap
The tap operator in RxJS is specifically designed for performing side effects (such as logging, making API calls, or modifying data) in an Observable chain.
You are building a dashboard and have created a "UserCard" component to display user details. You want this component to display user details differently based on the type of user (Admin, Guest, Registered). Which feature of Angular components can help you achieve this without creating multiple components?
- Component Inheritance
- Content Projection
- Interpolation
- Structural Directives
In this scenario, Structural Directives like *ngIf and *ngSwitch allow you to conditionally render content within a single component, enabling you to display user details differently based on the type of user.
You want to track the time taken for a user to navigate from one page to another in your Angular application. Which Router Events can be useful for this purpose?
- NavigationEnd and RoutesRecognized
- NavigationStart and NavigationCancel
- NavigationStart and NavigationEnd
- NavigationStart and NavigationError
To track the time taken for navigation, you can use NavigationStart and NavigationEnd Router Events. The NavigationStart event marks the start of navigation, and NavigationEnd marks the end. Combining them allows you to measure the time taken.