static-cms/packages/netlify-cms-backend-test/src/AuthenticationPage.js

import React from 'react';
import PropTypes from 'prop-types';
import ImmutablePropTypes from 'react-immutable-proptypes';
import { Icon } from 'netlify-cms-ui-default';

export default class AuthenticationPage extends React.Component {
  static propTypes = {
    onLogin: PropTypes.func.isRequired,
    inProgress: PropTypes.bool,
    config: ImmutablePropTypes.map.isRequired,
  };

  componentWillMount() {
    /**
     * Allow login screen to be skipped for demo purposes.
     */
    const skipLogin = this.props.config.getIn(['backend', 'login']) === false;
    if (skipLogin) {
      this.props.onLogin(this.state);
    }
  }

  handleLogin = (e) => {
    e.preventDefault();
    this.props.onLogin(this.state);
  };

  render() {
    const { inProgress } = this.props;

    return (
      <section className="nc-githubAuthenticationPage-root">
        <Icon className="nc-githubAuthenticationPage-logo" size="500px" type="netlify-cms"/>
        <button
          className="nc-githubAuthenticationPage-button"
          disabled={inProgress}
          onClick={this.handleLogin}
        >
          {inProgress ? "Logging in..." : "Login"}
        </button>
      </section>
    );
  }
}