stateComponent.js

class EmployeeDetails extends React.Component {
  constructor() {
    super();
    this.state = {
      name: "Mayank",
      age: 31,
      designation: "Senior Developer"
    }
  }
  
  updateEmployeeAge = () => {
    this.setState({
      age: this.state.age + 1
    });
  }
  
  render() {
    return (
      <div>
        <p>Employee Name: {this.state.name}</p>
        <p>Employee Age: {this.state.name}</p>
        <p>Employee Designation: {this.state.designation}</p>
        <input type="button" onClick={this.updateEmployeeAge} value="Click To Update Age" />
      </div>
    )
  }
}