JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.s3.yandex.net/react/libs/react.development.js"></script>
<script src="https://code.s3.yandex.net/react/libs/react-dom.development.js"></script>
<script src="https://code.s3.yandex.net/react/libs/babel.min.js"></script>

<div id="root"></div>

CSS

#root {
  display: flex;
  height: 50vh;
  margin: 0 auto;
  font-family: Helvetica, Arial, sans-serif;
  overflow: hidden;
}

body {
  padding: 0;
  margin: 0;
}

.content {
  display: flex;
  width: 100%;
}

.aside {
  background: #f00;
  height: 100%;
  flex: 0 0 200px;
}

.content__button {
  width: 200px;
  height: 64px;
  background-color: #1a1b22;
  font-style: normal;
  font-weight: normal;
  font-size: 24px;
  line-height: 24px;
  text-align: center;
  color: #fff;
  border: none;
  outline: none;
  margin: 26px auto auto;
  cursor: pointer;
}

React

class SettingsMenu extends React.Component {
  state = {
    theme: "dark",
    userSettings: {
      notificationsEnabled: true,
      sidebar: {
        title: "Боковая панель",
        enabled: false
      }
    }
  };

  toggleSidebar = () => {
    this.setState((prevState) => ({
      ...prevState,
      enabled: !this.state.enabled;
    }));
  };

  render() {
    const { enabled } = this.state.userSettings.sidebar;
    return (
      <>
        {enabled && <aside className="aside" />}
        <section className="content">
          <button className="content__button" onClick={this.toggleSidebar}>
            {enabled ? "Выключить" : "Включить"}
          </button>
        </section>
      </>
    );
  }
}

ReactDOM.render(<SettingsMenu />, document.querySelector("#root"));