first recurring

let arr1 = [2,5,1,2,3,5,1,2,4];
let arr2 = [2,1,1,2,3,5,1,2,4];
let arr3 = [2,3,4,5];
let arr4 = [2,5,5,2,3,5,1,2,4];
//It should return 1
function firstRecurring(arr)
{
    let hash = []; 
    for(let i of arr)
    {
        if(!hash[i])
        hash[i] = [i,0];
        else
        return i; 
        
        
    }
}
console.log(firstRecurring(arr1));
console.log(firstRecurring(arr2));
console.log(firstRecurring(arr3));
console.log(firstRecurring(arr4));