import React, { Component } from 'react';
import SweetAlert from 'sweetalert2-react';

// ...

render() {
  return (
    <div>
      <button onClick={() => this.setState({ show: true })}>Alert</button>
      <SweetAlert
        show={this.state.show}
        title="Demo"
        text="SweetAlert in React"
        onConfirm={() => this.setState({ show: false })}
      />
    </div>
  );
}

import React, { Component } from 'react';
import { withSwalInstance } from 'sweetalert2-react';
import swal from 'sweetalert2';

const SweetAlert = withSwalInstance(swal);

// ...

render() {
  return (
    <div>
      <button onClick={() => this.setState({ show: true })}>Alert</button>
      <SweetAlert
        show={this.state.show}
        title="Demo"
        text="SweetAlert in React"
        onConfirm={() => this.setState({ show: false })}
      />
    </div>
  );
}