React

HTML

<div id="app"></div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

.done {
  color: rgba(0, 0, 0, 0.3);
  text-decoration: line-through;
}

input {
  margin-right: 5px;
}

React

class Test extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
    	data: {
      	key: 'value',
        key2: 'value2',
        key3: 'value3'
      }
    }
  }
  
  render() {
    return (
      <ul>
        { Object.entries(this.state.data).map(([key, value]) => <li key={key}>{key}: {value}</li>) }
      </ul>
    )
  }
}

ReactDOM.render(<Test />, document.querySelector("#app"))