function makeRow(v=0){
            const array = new Array(3);
            array.fill(v);
            return array;
        }

        function makeMatrix(v = 0){
            const array = new Array(3)
            array.fill(makeRow(v))

            return array;
        }

        const a = makeMatrix()
        a[0][1]=2
        console.log(a)
        /*
        [
          [0,2,0],
          [0,2,0],
          [0,2,0]
        ]
        */
        

as in the code above, why did I only manipulate item 0 of a, but the result is that each item has been changed
for a big solution