function randomize(param1, param2, callback) {
	if (typeof callback === 'function') {
		let num1 = parseInt(param1);
		let num2 = parseInt(param2);

		callback(num1, num2);
	} else {
		console.log('Błąd!!');
	}
}

randomize(1, '2', function (num1, num2) {
	console.log(Math.random() * (num2 - num1) + num1);
});