How to handle events using expressions inside JSX?

The App component returns a button to the content and used the onClick prop to tell React how to respond when the click event is triggered. The button element is configured using the onClick prop, which tells React to invoke the calculate method in response on the click event.


import React, { Component } from 'react';
class App extends Component {
constructor(props) {
    this.state = {
        len: 4,
        bre: 5,
        area: 0
calculate = () => this.setState({ area: this.state.len * this.state.bre});
render = () =>
    <span class="d-block p-2 bg-dark text-white">
        <button className="btn btn-info m-2" onClick={ this.calculate }>
            Click Me
        Calculate Area: { this.state.area }
export default App;
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