React - Basics Tutorial

ReactJS Component state

In React, component state refers to an object that holds data, representing the current state of a component. It allows you to manage and track changes in the component’s data over time, which results in rendering updates to the user interface.

The state of a component can be initialized in the component’s constructor using the this.state property. For example:

class MyComponent extends React.Component {
  constructor(props) {
    this.state = {
      count: 0,
      isLoading: true,
      error: null,

  render() {
    // JSX code

In the above example, we have initialized the state object with three properties: count, isLoading, and error. These properties can be accessed and updated using this.state.propertyName.

To update the state, React provides the setState() method. It is used to modify the component’s state and trigger a re-render of the component. Here’s an example of updating the count state property:

this.setState({ count: this.state.count + 1 });

It’s important to note that setState() is asynchronous, so React may batch multiple state updates together for better performance. If the new state relies on the previous state, it’s advisable to use the callback syntax of setState() to ensure the correct state transition. Here’s an example:

this.setState((prevState) => ({
  count: prevState.count + 1,

By updating the state, React knows that the component needs to be re-rendered, and the changes in the state will be reflected in the UI.

Working with component state allows you to build dynamic and interactive user interfaces in React. It enables you to manage and control the behavior of your components based on user interactions, server responses, or any other change in the application’s data.

Leave a Reply