export function func() {
    const test = new Array(2).fill(new Array(2))
    
    for (let i = 0; i < test.length; i++) {
        test[i][0] = i;
    }
    
    console.log(test)
  return -1;
}

gives me [[1, undefined], [1, undefined]] instead of [[0, undefined], [1, undefined]]

So confused as to why can anyone explain? Or am I missing something obvious?