@sindresorhus/class-names/index.js

Conditionally join CSS class names together - Especially useful with React

export default function classnames(...arguments_) {
	const result = new Set();

	for (const item of arguments_) {
		const type = typeof item;

		if (type === 'string' && item.length > 0) {
			result.add(item);
		} else if (type === 'object' && item !== null) {
			for (const [key, value] of Object.entries(item)) {
				if (value) {
					result.add(key);
				}
			}
		}
	}

	return [...result].join(' ');
}