function firstRecurringCharacter(arr) { const map = new Map(); for( i = 0; i < arr.length; i++) { console.log(map[arr[i]]); if(!map[arr[i]]) { map[arr[i]] = true; } else { return map[arr[i]]; } } return undefined; } console.log(firstRecurringCharacter([2,3,5,7,8,2]));