Are custom DOM attributes supported in React v16?
Assesses fundamental understanding of React conventions, runtime behavior, and memory/performance considerations.
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Note: This question references React v16, which is outdated. The information below applies to React 16+, including current versions (React 18/19).
Yes. Starting with React 16, React no longer ignores unknown DOM attributes. If you write JSX with an attribute that React doesn't recognize, React will pass it through to the DOM.
For example, let's take a look at the below attribute:
```jsx harmony
<div mycustomattribute={"something"} />
In React 15 and earlier, this would render an empty div:
<div />
In React 16 and later (including React 18/19), any unknown attributes will end up in the DOM:
<div mycustomattribute="something" />
```
This is useful for supplying browser-specific non-standard attributes, trying new DOM APIs, and integrating with opinionated third-party libraries.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.