clone.js

function clone(obj) {
	if (!obj || typeof obj !== 'object') {
		return obj;
	}
	if (obj instanceof Date) {
		return new Date(obj.getTime());
	}
	
	var result,
		propertyIndex,
		propertyCount,
		propertyKey,
		propertyValue,
		empty = {};
		
	if (obj instanceof Array || typeof obj === 'array') {
		result = [];
		for (; propertyIndex < propertyCount; propertyIndex++) {
			result.push(clone(obj[propertyIndex]));
		}
		return result;
	} else {
		result = obj.constructor ? new obj.constructor() : {};
		
		for (propertyKey in obj) {
			propertyValue = obj[propertyKey];
			
			if (propertyKey in result) {
				if (result[propertyKey] !== propertyValue
					&& (!(propertyKey in empty) || empty[name] !== propertyValue))
				{
					result[propertyKey] = propertyValue;
				}
			} else {
				result[propertyKey] = propertyValue;
			}
		}
	}
	
	return result;
}