※This article is a repost from Innovator Japan Engineers’ Blog.

Preparation

Setting up the build environment can be cumbersome, so this time we will use the official Facebook tool create-react-app.

npm install -g create-react-app

We will prepare the environment with the app name md-editor.

create-react-app md-editor

Next, let's install the libraries we will use this time.

cd ./md-editor

npm install --save marked

npm install

Finally, once the server is started, we are ready to go. npm start

Implementation

STEP 1

Before we start implementing, let's delete the unnecessary files that we won't be using this time.

• App.css
• App.test.js
• logo.svg

Make sure to remove the imports for these files from src/index.js and src/App.js.

Also, in src/App.js, let's leave the contents of the return statement empty. (We will ignore the warning during build about the return statement being empty for now.)

src/index.js

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import registerServiceWorker from './registerServiceWorker';

ReactDOM.render(<App/>, document.getElementById('root'));
registerServiceWorker();

src/App.js

import React, {Component} from 'react';

class App extends Component {
  render() {
    return ();
  }
}

export default App;

STEP 2

Create a file named Markdown.js under the src directory. We will implement the markdown component in this file.

src/Markdown.js

import React, {Component} from 'react';
import ReactDOM from 'react-dom';
import marked from 'marked';

class Markdown extends Component {
  constructor(props) {
    super(props);
    this.state = {
      html: ''
    };

    this.updateMarkdown = this.updateMarkdown.bind(this);
  }

  updateMarkdown(event) {
    this.setState({
      html: marked(event.target.value)
    });
  }

  render() {
    const html = this.state.html;

    return (<div>
      <h1>Markdown Input</h1>
      <textarea onChange={this.updateMarkdown}></textarea>
      <h1>Markdown Output</h1>
      <div dangerouslySetInnerHTML={{
          __html: html
        }}></div>
    </div>);
  }
}

export default Markdown;

It's just a few lines. This will function as a markdown editor. It's almost raw JS. The only thing specific to React is JSX.

STEP 3

Finally, let's import Markdown.js into App.js.

import React, {Component} from 'react';
import Markdown from './Markdown';

class App extends Component {
  render() {
    return (<Markdown/>);
  }
}

export default App;

Verification

If you want to highlight the source code, you can customize marked using isagalaev/highlight.js - github for a better experience.

References

• chjj/marked
• React.Component - React
• super - MDN

Repository

The source code is available at bmf-san/til/javascript/md-editor/ - github.

Thoughts

I like React because it allows coding in a way that is close to raw JS, making it less likely to lock you into knowledge of the framework.

I have omitted most of the code explanations, but I think you can understand most of it by looking at the article Modern JS Discussion by @bmf_san.