First recurring counter

by Artem

JavaScript

'use strict';

const input = 'dbaba';

const solution1 = givenString => givenString.split('').find((el, index, arr) => arr.indexOf(el, index + 1) !== -1);
const solution2 = givenString => {
	const recSet = new Set();
	for (let sym of givenString) {
		if (recSet.has(sym)) return sym;
		recSet.add(sym);
	}
};

console.log(solution2(input));