20 Web Components Interview Questions and Answers

Web Components are a set of standards that allow developers to create reusable components for the web. These components are self-contained and can be used in any web application. With the popularity of web components growing, it is likely that you will encounter questions about them during a job interview. In this article, we review some of the most common questions about web components and how you should answer them.

Web Components Interview Questions and Answers

Here are 20 commonly asked Web Components interview questions and answers to prepare you for your interview:

1. What are web components?

Web components are a set of web technologies that allow you to create reusable custom elements that can be used in your web applications. With web components, you can create your own HTML tags, CSS styles, and JavaScript code that can be reused across your web applications.

2. What is the difference between a web component and an Angular component?

Angular components are a subset of web components. Web components are a set of standards that allow you to create reusable, self-contained, and independent HTML elements. Angular components are web components that have been created with the Angular framework.

3. What languages can be used to write web components?

Web components can be written in any language that can be compiled to JavaScript. This includes languages like TypeScript, Dart, and even plain old JavaScript.

4. How do you create custom elements using JavaScript?

You can create a custom element using the document.registerElement method. This method takes two arguments: the name of the element, and an object containing the element’s prototype.

5. Can you explain what Shadow DOM is in context with Web Components?

Shadow DOM is a DOM feature that allows you to encapsulate a part of the DOM inside of a Web Component, so that it is isolated from the rest of the document. This means that you can style the component without having to worry about affecting the rest of the document, and vice versa.

6. What are some of the advantages of using Web Components over other frameworks like Angular or React?

Some advantages of using Web Components over other frameworks include:
-Web Components are framework agnostic, meaning they can be used with any framework or no framework at all.
-Web Components are self-contained, meaning they are self-contained units that can be reused as needed.
-Web Components are easy to use, meaning they are easy to implement and use in your own web projects.

7. Are there any limitations to using Web Components?

While Web Components are incredibly powerful, there are a few potential limitations to be aware of. One is that not all browsers support all of the features of Web Components yet, so you may need to use polyfills or other workarounds to get your components to work in older browsers. Additionally, because Web Components are still relatively new, there is not yet a lot of documentation or community support available, so you may need to do some extra research to figure out how to use them effectively.

8. What are Custom Elements and how are they different from regular HTML tags?

Custom Elements are a web component specification that allows developers to create their own HTML tags. These custom tags can then be used in HTML documents just like any other HTML tag. The difference is that Custom Elements are defined by the developer, so they can include any desired functionality. This makes them much more powerful and flexible than regular HTML tags.

9. What are Templates and when should you use them?

Templates are a way to create reusable HTML fragments that can be inserted into a document at runtime. This can be useful for creating things like custom elements or repeating content.

10. Are there any differences between Shadow DOM v0 and v1?

Yes, there are a few key differences between Shadow DOM v0 and v1. The biggest difference is that Shadow DOM v1 introduces a new concept called “slots” which allows for more flexible composition of elements. Shadow DOM v0 did not have this concept, which could lead to issues when trying to compose complex elements. Additionally, Shadow DOM v1 also introduces a new way to style elements via the :host-context() pseudo-class. This pseudo-class allows for styling based on where an element is located in the DOM, rather than just its immediate parent.

11. Is it possible to pass data as attributes to our custom element? If yes, then how?

Yes, it is possible to pass data as attributes to our custom element. We can do this by using the setAttribute() method.

12. What are Slots and why are they useful?

Slots are a way to define where content from outside of a web component should be inserted into the component’s DOM. This is useful for creating reusable components that can be used in a variety of contexts. Slots make it easy to insert different content into a component without having to rewrite the component itself.

13. How do you decide which framework to use for building your application? What factors come into play?

The decision of which framework to use for building an application can be a difficult one. There are many different factors that come into play, such as the size and complexity of the application, the team’s experience and expertise, the project timeline, and the budget. Ultimately, it is important to choose a framework that will best support the needs of the application.

14. What is Polymer and how is it related to Web Components?

Polymer is a library that helps developers create custom HTML elements, which are a type of web component. Polymer makes it easy to create these custom elements, and also provides a number of features that are not available in vanilla web components.

15. What is StencilJS? Why would we want to consider using it instead of other frameworks and libraries?

StencilJS is a web component compiler. That means it takes the code you write for your web components and compiles it into standard JavaScript that can run on any platform. The benefits of using StencilJS are that it can help improve performance and make your web components more portable.

16. When is it better to use CSS Variables than LESS/SASS variables?

There is no definitive answer to this question, as it depends on the specific situation and what you are trying to achieve. In general, however, CSS Variables may be a better choice when you need to dynamically update the value of a variable (based on user input, for example), or when you want to keep the CSS code itself relatively simple. LESS and SASS variables may be a better choice when you need more control over the CSS output, or when you are working with a large number of variables.

17. What is the best way to build and package web components?

The best way to build and package web components is to use a tool like Polymer or AngularJS. These tools will help you create reusable components that can be easily shared and used by other developers.

18. What are some ways to make sure that web components load quickly on mobile devices?

One way to make sure that web components load quickly on mobile devices is to use a server-side rendering solution. This will allow the web components to be rendered on the server before they are sent to the client. Another way to improve loading times is to use a bundling tool to package all of the web components into a single file. This will reduce the number of HTTP requests that need to be made.

19. What’s the difference between Reusable Component Libraries and Design Systems?

Reusable component libraries are collections of components that can be used to build user interfaces. Design systems are collections of reusable components, along with guidelines and best practices for using them, that can be used to build consistent, high-quality user interfaces.

20. Are there any limits to the number of web components that can be included in a page?

There are no hard limits to the number of web components that can be included in a page, but performance may start to suffer if there are too many. It is generally recommended to keep the number of web components down to a few dozen or so per page.