Fill Matrix - B

let matrixSize = +gets();

let matrix = Array.from(Array(matrixSize), () => new Array(matrixSize).fill(0));

//col     0 1 2
//row 0 - 1 6 7
//row 1 - 2 5 8
//row 2 - 3 4 9

let num = 1;
for(let coll = 0; coll < matrixSize; coll++){
    if(coll % 2 === 0){
        for(let row = 0; row < matrixSize; row++){
            matrix[row][coll] = num;
            num++
        }
    }else{
        for(let row = matrixSize-1; row >= 0; row--){
            matrix[row][coll] = num;
            num++
        }
    }
}

for(let coll = 0; coll < matrixSize; coll++){
    console.log(matrix[coll].join(' '));
}