What is the difference between constructor and getInitialState?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of React conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
You should initialize state in the constructor when using ES6 classes, and getInitialState() method when using React.createClass().
Using ES6 classes:
class MyComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
/* initial state */
};
}
}
Using React.createClass():
const MyComponent = React.createClass({
getInitialState() {
return {
/* initial state */
};
},
});
Note: React.createClass() is deprecated and removed in React v16. Use plain JavaScript classes instead.
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.