Are you an aspiring React developer preparing for his/her first interview these days? Then you must be dying to know what React interview questions they're most likely to ask you.
What are the most predictable talking points that you should prepare yourself for?
For whether you're:
- an experienced front-end developer
- or a junior developer — wannabe React developer — who's just entered the “realm” of JavaScript
… you'd give anything to know which vital concepts your interviewers will use as main criteria for assessing whether you're the knowledgeable React developer they need.
Or you still have a lot of React learning to do...
Now, to put an end to your “turmoil”, I've put together a list of 10 React interview questions (both basic and advanced) that you should expect to be asked:
1. How Does React Set Itself Apart from Other Frameworks?
How you'll answer this question will help you level up from "just another wannabe React developer” to a truly valuable candidate. One with an above-the-average understanding of the library, who can articulate intelligent options.
Comparing React to other JavaScript libraries is going to drive their attention to both:
- your experience as a front-end developer, one who's more than just “familiar with” developing in other libraries, as well
- and your deep knowledge of React
Since it's only a certain experience in working with it that can enable you to identify key differences between React and other frameworks:
For instance, React's focus on creating UI components vs having to develop the app's whole architecture (like it's the case with Angular).
Note: needless to add that using examples from your own experience is always a winning card to play:
Have you migrated an app, that was originally written in another library, to React? Do share relevant glimpses from your experience with your interviewer(s)!
Focus on the key differences between working with the other JS library and with React that you've identified yourself.
2. What's Your Favorite React Stack and Why?
Do expect open, non-specific React interview questions like this one, as well!
Not only do their breathe life into an otherwise overly technical and rigid interview, but it will help the interviewer get a clear picture on:
How you can justify your choices and preferences by backing them up with clearly articulated arguments.
Word of caution: Honesty's your best friend (if not the only one)! You might be tempted to choose dependencies that you have no (or little) experience working with, just because they're popular: do not fall into this trap!
You'll only risk getting tangled up in your lies if the interviewer decides to ask you for further, more specific details about your experience working with those tools.
3. React Interview Questions: What Are React.js Components?
This is THE question on the “checklist" of every interviewer looking for a React developer.
Therefore, coming up with an accurate definition is crucial:
React components are reusable, independent “puzzle pieces” making up the UI!
This could be a viable, to-the-point type of definition. Take it from here and enrich it:
- components in React accept arbitrary inputs (or “props”)
- … can be handled as isolated pieces
- they return React elements that describe precisely what should get displayed on the screen
4. What Are the 3 Main Stages in a React Component's Lifecycle?
It's only but... critical for a React developer worth his salt to know which are the 3 general parts of a component's lifecycle:
Proving that you do know them, will only assure your interviewers that you'll know what specific logic you'll need to apply at each one of these 3 stages:
- Initialization
- State/Property updates
- Destruction
Being able to identify these 3 “lifecycle methods” — defining the way a component manages its state, properties and rendered output — enables you to run the right code at precisely the right times in a React project's development process.
5. What Is Virtual DOM and How Does React Use It?
This must be one of the most predictable React interview questions. Therefore:
Be prepared and... prepare for answering it with a clearly articulated definition.
You could start by attempting at a definition of the DOM itself:
DOM (Document Object Model or HTML Model) is an abstraction (or an “in-memory representation) of HTML structured code. The structure — where elements, along with their attributes, and content are listed as objects and properties — inside which developers create documents and modify content as needed.
Now, as for the Virtual DOM:
It's an abstraction of an abstraction — a representation (or lightweight copy) of DOM objects.
But how does React use Virtual DOM to render an app's UI?
The main idea around React's Virtual DOM is that it's precisely this copy of the real DOM that the library updates first. Before it applies any changes to the real DOM itself.
In other words: if state changes in a component, React runs a “diffing” algorithm first, detecting the changes in the virtual DOM. And it's only after it has got the results (using the “reconciliation” method) of this diffing process that it updates the “real” DOM.
Then, it will be the perfect time to point out the virtual DOM's impact on any React app's overall performance...
To be continued...