First Recuring Character

//Brute force method
function firstRecuringCharacter(input){
    for(let i=0;i<input.length;i++){
        for(let j=i-1;j>=0;j--){
            if(input[j]===input[i]){
                return input[i]
            }
        }
    }
    return undefined
}

//Optimal Solution using Hash Table
function firstRecuringCharacter1(input){
    let map={};
    for(let i=0;i<input.length;i++){
        if(map[input[i]]!=undefined){
            return input[i]
        }else{
            map[input[i]]=i
        }
    
    }
    return undefined
}

firstRecuringCharacter1([1,1,3,3])