CodeSkill2-3.js

var tablica_1 = [1,2,3,4,6],
	tablica_2 = [3,1,5,6],
	tablica_3 = [3,1,2,3,6],
    	tablica_4 = [3,5,6];

function contains(array, item) {
	return array.indexOf(item) !== -1;
}

function head(array) {
	return array[0];
}

function rest(array) {
	return array.slice(1);
}

function findCommonElements (...arrays){
	var result = head(arrays).filter(
		item => 
			rest(arrays).find(
				array => !contains(array, item)
			) === undefined
	});
	console.log(result);
}

//test
findCommonElements (tablica_1,tablica_2,tablica_3);
findCommonElements (tablica_1,tablica_2,tablica_3,tablica_4);