Object.prototype.isClass = function(className) {
	return this.constructor == eval('new '+className+'().constructor');
//	return this.__proto__ == eval(className + '.prototype');
}

function isFunction(a) {return typeof a == 'function'}
function isObject(a) {return (a && typeof a == 'object') || isFunction(a)}
function isArray(a) {return isObject(a) && a.constructor == Array}
function isString(a) {return typeof a == 'string'}
function isClass(a, className) {return isObject(a) && a.isClass(className)}