typesript, dealing with accumulating outside scope

example.ts

/*
error
Line 6: Char 14: error TS2448: Block-scoped variable 'res' used before its declaration.
*/

/* code */
function longestCommonSubsequence(arrays: number[][]): number[] {
    // have a ptr for each array
    let res = new Set();
    let setA = new Set<number>(arrays[0]);
    for (let i=1; i < arrays.length; i++) {
        if (!res) {
            res = setA;
        }
        let setB = new Set<number>(arrays[i]);
        let res = res.intersection(setB)
    }
    console.log(res)
    // increment each ptr keeping track of any common subsequence
    return [3]
};

solution on tsplay https://tsplay.dev/Woe4pN