classNames util example

Switch.js

const classNames = (...classes) => classes.filter(Boolean).join(' ');

// No need to default to an empty string as className
function Switch({on, className, ...props}) {
  return (
    <div className="toggle">
      <input
        className="toggle-input"
        type="checkbox"
      />
      <button
        className={classNames(
          className,
          'toggle-btn',
          on && 'toggle-btn-on',
          !on && 'toggle-btn-off'
        )}
        {...props}
      />
    </div>
  )
}