Angular Interview Question Set 4
What are the distinct types of Angular filters?
Filters are a part of Angular that helps in formatting the expression value to show it to the user. They can be added to services, directives, templates, or controllers. You also have the option to create personalized filters as per requirements. These filters allow you to organize the data easily such that only the data that meets the respective criteria are displayed. Filters are placed after the pipe symbol ( | ) while used in expressions.
How can one create a service in Angular?
Service in Angular is an object that can be substituted. It is wired and combined with the help of dependency injection. Services are developed by getting registered in a module that they need to be executed in. The three methods of creating a service in Angular are as follows:
What does subscribing mean in RxJS?
In RxJS, when using observables, we need to subscribe to an observable to use the data that flows through that observable. This data is generated from a publisher and is consumed by a subscriber. When we subscribe to an observable, we pass in a function for the data and another function for errors so that, in case there is some error, we can show some message or process the message in some way.
What is Angular Router?
Routing in a single-page frontend application is the task of responding to the changes in the URL made by adding and removing content from the application. This is a complicated task as we first need to intercept a request that changes the browser’s URL as we do not wish for the browser to reload. Then, we need to determine which content to remove and which content to add, and finally, we have to change the browser’s URL as well to show the user the current page they are on.
What is REST?
REST in Angular stands for Representational State Transfer. It is an API that works on the request of HTTP. Here, the requested URL points to the data that has to be processed, after which an HTTP function is used to identify the respective operation that has to be performed on the data given. The APIs that follow this method are referred to as RESTful APIs.
What is the scope?
A scope is an object in Angular referring to the application model. It is a context for executing expressions. These scopes are organized in a hierarchical form that is similar to the application’s DOM structure. A scope helps in propagating various events and watching expressions.
Explain Angular CLI.
Angular CLI is otherwise known as Angular command-line interface. Angular supports CLI tools that give professionals the ability to use them to add components, deploy them instantly, and perform testing and many such functions.
What is HttpClient, and what are its benefits?
HttpClient is an Angular module used for communicating with a backend service via the HTTP protocol. Usually, in frontend applications, for sending requests, we use the fetch API. However, the fetch API uses promises. Promises are useful, but they do not offer the rich functionalities that observables offer. This is why we use HttpClient in Angular as it returns the data as an observable, which we can subscribe to, unsubscribe to, and perform several operations on using operators. Observables can be converted to promises, and an observable can be created from a promise as well.
What is multicasting in Angular?
In Angular, when we are using the HttpClient module to communicate with a backend service and fetch some data, after fetching the data, we can broadcast it to multiple subscribers, all in one execution. This task of responding with data to multiple subscribers is called multicasting. It is specifically useful when we have multiple parts of our applications waiting for some data. To use multicasting, we need to use an RxJS subject. As observables are unicast, they do not allow multiple subscribers. However, subjects do allow multiple subscribers and are multicast.
What is a directive in Angular?