Anyways

Let's go for a strategy to minimize the threshold.

React on CodePen-React Patterns & Templates

Choose a good teaching material.

Codepen

Appropriately made it easy to use.
A Pen by yumainaura

point

I'm making a generic module called Box

Calling 3 Box Components from App Component

changing colorMode

I have defined colorMode in CSS

When colorMode = false, it seems that you can do nothing.
(Don't feel like being similar to # ruby's bogus operator)

js

// This is how a function component takes props.
const Box = props => (
  <div className={`box ${props.colorMode}`}>
    <h1 className="title">{props.title}</h1>
  </div>
);

// This Class component also can have props
class App extends React.Component {

  render() {

    return <div>
      <h1 class="subtitle">
        {this.props.header}
      </h1>
      <Box
        colorMode="false"
        title="Light"
      />
      <Box
        colorMode="dark-mode"
        title="Dark"
      />
      <Box
        colorMode="orange-mode"
        title="Orange"
      />
    </div>;
  }

}


ReactDOM.render(<App header="Hello, Colors!"/>, document.getElementById("root"));

css

body {
  height: 100vh;
  margin: 0;
  display: grid;
  place-items: center;
  max-width: 250px;
  margin: 0 auto;
}
.box {
  width: 300px;
  &.dark-mode {
    background: black;
    color: #bbb;
    h1 {
      color: white;
    }
    .checkbox:hover {
      color: white;
    }
  }
  &.orange-mode {
    background: orange;
    color: red;
    h1 {
      color: red;
    }
    .checkbox:hover {
      color: red;
    }
  }
}

HTML

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

Original by Github issue