React Answers

What is the difference between using constructor vs getInitialState in React / React Native?

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In React, there’s a fundamental difference between using constructor and getInitialState:


In class components, the constructor method is a standard JavaScript constructor that gets called when a component is instantiated.

It’s used for initializing state, binding event handlers, and other setup operations.

We explicitly define the initial state within the constructor by assigning an object to this.state.

If we want to use instance properties or methods, we would typically define them within the constructor.


class MyComponent extends React.Component {
  constructor(props) {
    this.state = { count: 0 };
  render() {
    return <div>{this.state.count}</div>;


getInitialState is a method used in React’s older API, particularly in createClass syntax, which is now deprecated.

It’s used exclusively for initializing the state of a component.

When using getInitialState, we return an object representing the initial state of the component.

This method is not available in modern React versions (React 16.3 and later), and we should use the constructor for state initialization instead.

Example (using createClass, not recommended for modern React):

const MyComponent = React.createClass({
  getInitialState() {
    return { count: 0 };
  render() {
    return <div>{this.state.count}</div>;

In summary, constructor is a standard JavaScript method used for various initialization tasks, including state initialization in class components, while getInitialState is an older React API used for initializing state, particularly in createClass syntax, which is deprecated in modern React versions. For new projects and modern React components, we should use constructor for state initialization.

By John Au-Yeung

Web developer specializing in React, Vue, and front end development.

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