An improved React cx.js that supports nested arrays, which allows for dynamic keys

cx.js

// Improved on react/lib/cx.js
// by supporting nested arrays to allow for dynamic keys

function cx(classNames) {
	if(classNames instanceof Array) {
		var filteredClasses = [];
		classNames.forEach(function(className, i) {
			if(typeof className === 'string') {
				filteredClasses.push(className);
			}
			else if(typeof className[1] === 'undefined' || !!className[1]) {
				filteredClasses.push(className[0]);
			}
		});
		return Array.prototype.join.call(filteredClasses, ' ');
	}
	else if(typeof classNames === 'object') {
		return Object.keys(classNames).filter(function(className) {
			return classNames[className];
		}).join(' ');
	} else {
		return Array.prototype.join.call(arguments, ' ');
	}
}

module.exports = cx;

gistfile1.js

// Basic example of how to use the Array-based syntax.
// Note the optional nested arrays, where the string is assumed as truthy

{
	className: cx([
		'block',
		['block--active', this.state.isActive],
		'block--key' + key
	])
}