Create simple animated expander in React

Hi there! 👋 😊

Today, I was thinking about creating an animated expander in React and I came up with the following solution.

Effect of this short post:

In the example below, I create a simple expander that displays Fruits 🍉 and Vegetables 🍅 lists on click event. I've used a modern approach that involves the use of functional components and React hooks. In this case useState hook stores the state of my expander. 🔺🔻

Runnable example:

// ONLINE-RUNNER:browser;

//Note: Uncomment import lines during working with JSX Compiler.
// import React from 'react';
// import ReactDOM from 'react-dom';

const expanderStyle = {
    margin: '6px 0',
    padding: '2px',
    border: '1px solid #85C1E9'
};

const headerStyle = {
	display: 'flex',
    cursor: 'pointer'
};

const titleStyle = {
    padding: '3px',
	flex: 'none'
};

const spacerStyle = {
	flex: '1'
};

const iconStyle = {
	padding: '3px',
	flex: 'none'
};

const contentStyle = {
	overflow: 'hidden',
    transition: 'all 0.3s'
};

const contentExpandedStyle = {
    ...contentStyle,
    padding: '4px 0',
    border: '1px solid #85C1E9',
    height: 'auto',
    filter: 'opacity(1)'
};

const contentCollapsedStyle = {
    ...contentStyle,
  	padding: '0 0',
    border: '1px solid transparent',
    height: '0',
    filter: 'opacity(0)'
};

const Expander = ({title, children}) => {
    const [expanded, setExpanded] = React.useState(false);
    const handleHeaderClick = () => {
    	setExpanded(expanded => !expanded);
    };
  	return (
      <div style={expanderStyle}>
        <div style={headerStyle} onClick={handleHeaderClick}>
          <div style={titleStyle}>{title}</div>
          <div style={spacerStyle} />
          <div style={iconStyle}>{expanded ? '🔺' : '🔻'}</div>
        </div>
        <div style={expanded ? contentExpandedStyle : contentCollapsedStyle}>
          {children}
        </div>
      </div>
    );
};

// Usage example:

const App = () => {
  return (
    <div style={{height: '260px'}}>
      <Expander title="🍏🍌🍊 Fruits">
        <ul>
          <li>🍏 Apple</li>
          <li>🍌 Banana</li>
          <li>🍊 Orange</li>
        </ul>
      </Expander>
      <Expander title="🥕🥒🍅 Vegetables">
        <ul>
          <li>🥕 Carrot</li>
          <li>🥒 Cucumber</li>
          <li>🍅 Tomato</li>
        </ul>
      </Expander>
    </div >
  );
};

const root = document.querySelector('#root');
ReactDOM.render(<App/>, root );

References

• React - simple animated expander example

• Introducing Hooks