Angular is a front-end framework developed by futuristic brains at Google. The framework debuted in 2010, and since then, it has been open-source. Even today, a team of developers at Google and many other open-source contributors maintain the framework and regularly bring security and feature updates. While it was discontinued, a new version named Angular was introduced, and since then, it has been the first choice of many developers.
Going forward, we will have a look at the top 10 interview questions and answers. Whether you are preparing for giving an interview or taking an interview, these questions will help you in your journey to acquire a new job or find the right candidate. So let’s get started without wasting much time.
Top 10 Angular Interview Questions and Answers in 2022
1. Which lifecycle hooks are available in Angular?
Multiple lifecycle hooks are available in Angular, and each of them has a separate functionality. Let’s discuss a few of them.
ngOnInit()
ngOnInit() is the lifecycle hook that runs once for every angular component. Whenever an initialization request for a component is received, the ngOnInit() hook is executed. You can consider this as the constructor for an angular component. This is the ideal place to initialize variables for a component and connect to databases if there’s a need to do so.
ngOnChanges()
This lifecycle method determines what to do with changes. As the name suggests, this lifecycle hook is run every time a change is received. You can put in validation functionalities in this method to ensure that every data that changes is valid for your application.
ngOnDestroy()
Just like ngOnInit(), the ngOnDestroy() lifecycle hook is called once per Angular component. This lifecycle method determines the actions to be taken when a component is destroyed. Releasing of resources and disconnecting from the database are the common activities that are performed in this lifecycle method.
2. What are ng-if, ng-show, and ng-hide in Angular?
Angular has plenty of directives that make coding easier, and three of them are ng-if, ng-show, and ng-hide. All these are related to rendering and showing DOM elements, so let’s understand them better.
Ng-if
Ng-if is the Angular if condition for DOM elements. This directive shows the content if a condition is true. If the condition is false, the directive just does not render the content.
Ng-show
Ng-show is another DOM directive of Angular. It renders and shows the DOM element if the expression evaluates to true. If you use ng-show, the element will always be rendered on the page, but it will be hidden from view if the expression evaluates to false.
Ng-hide
As the name suggests, the ng-hide directive is used to hide DOM elements in Angular apps. Using this app, you can hide the element whenever the expression evaluates to true.
3. What is a route in Angular? How to define routes in an Angular application?
Angular supports routing, and this enables developers to craft single-page applications with multiple URLs and Views. To create routes in the Angular application, you have to use the ngRoute module and routeProvider.
There are two main methods to match the route. One is when(), and the other is otherwise(). Both methods are self-explanatory when the () method is used to define URLs and their corresponding views to be rendered. If no URL pattern matches the request URL, the URL specified in the otherwise() method is called.
4. What is $watch in Angular? When is it used?
When you want to watch the changes on a variable in an Angular app, you use the $watch feature. It carefully tracks the defined variable’s state and provides updates whenever the variable’s value is updated.
5. What are directives in Angular? Explain a few in-built directives of Angular
Directives in Angular provide a new behavior and functionality to the element to which they are attached. Directives are attached to DOM elements, and a few in-built directives are ng-model, ng-repeat, ng-show, ng-bind, etc.
Discussing more on ng-repeat and ng-show.
Ng-repeat
Ng-repeat is the Angular version of for loops. This directive helps you to repeat DOM elements. It is highly helpful in rendering tables and lists from received data.
Ng-show
Ng-show is a directive that helps developers to hide and show DOM elements based on a specific expression. If the expression evaluates to true, the corresponding DOM element will be shown; else, it will be hidden.
6. Does Angular provide logging functions? If yes, explain the different logging functions of Angular.
Yes, Angular comes with a built-in logging service, and it is quite helpful in creating and maintaining logs when your application runs. $log is the built-in service that is used, and it has many different functions for logging.
Different Logging Functions
log()
$log() is the primary and widely used logging function in Angular applications. The log() function is used for logging a message on the console of your angular application.
info()
Many informational messages are generated on application run times. info() function is used to write informational messages onto the console or other logging systems.
error()
Runtime errors are common, but keeping a log of them helps you find error traces faster and easier. The error() function is used to log error messages on the console of Angular apps.
7. What is data binding in Angular? Explain types of data binding and their benefits.
In Angular, data binding is a way using which data in the application is kept in sync. It allows the users to have the same data and eliminates inconsistency. Data binding ensures that data is the same, whether it is in the models or in the view.
The ng-model and ng-bind directives are used to ensure data binding in Angular. Unlike other frameworks, angular has two different ways of data binding, and it is vital to know them both.
One-Way Data Binding
As the name suggests, in one-way data binding, only a single side of the data is synced. In angular, when you use one-way data binding, the data is only synced when there is a change in the data on the model side.
If you have made any changes in the data on the view side, it will not sync instantly. Due to this, the view is not updated instantly, and there can be chances of data inconsistency if this is not implemented correctly.
Two-Way Data Binding
Two-way data binding ensures that your application data is always synced without the need to write extra code. In two-way data binding, the application considers the model data as a single source of truth. Hence, whenever there is an update or change in the model side, the view is re-rendered or updated to reflect the latest changes.
8. What are the primary features of Angular?
The primary features of Angular are as follows.
MVC Architecture
Angular applications support MVC architecture. Using this architecture, you can easily create better and highly scalable applications. Moreover, you can even have a large team of developers work on an identical product without causing any merge conflicts or any such issues. MVC architecture allows you to create different parts of the web app, like the front end and back end, in the same repository, even while working separately.
Data Binding
Angular provides excellent data binding with the use of ng-bind and ng-model directives. While the first directive provides one-way data binding, the ng-model directive allows you to implement Angular much revered two-way data binding.
Templates
Being based on the MVC architecture, Angular has a templating way. It uses templates to create views from your code when the model returns data. All this helps in dynamic content generation based on user requests.
Unit Testing
Angular is known for its automation testing capacities. If you know Angular well, you can write automated test cases that will run on each build and provide you with a report of your application’s stability and usefulness. The more tests you write, the better your final product emerges.
Routing
Angular helps in building single-page applications, but even there, it helps developers to create routes. The routeProvider in Angular is an in-built routing mechanism used in all major applications.
Filters
Angular does handle a lot of things on the front end itself. One such thing is filtering. It comes with in-built filters for various things so that you can filter data in the front end itself without relying on how the API has given the data.
9. What are filters in Angular?
Filters are a way to present data in a better way. In angular, you don't have to worry about how you receive the data from an API; you can always filter it and present it in the way you like on the client side.
Filters are commonly used to manipulate text and present numerical data in a specific way. You can use a pipe character after your variable and put the filter name to filter your data in the desired format.
10. Can parent controllers access the methods of child controllers in Angular?
Angular does not modify the rules of inheritance. In order to access the methods of a controller, the new controller needs to be a child of the old controller. Thus, a parent controller cannot access the methods of a child controller, but the reverse is possible.
There are many other topics in Angular that are brought up in interviews regularly. These are just some widely sought-after topics, and if you are an angular development agency that wants to take an in-depth interview or you want to prepare more for the interview, this list is just a starting point.