Equal opeartor not working with Array in Solidty

I wrote a simple solidity programme:-

//SPDX-License-Identifier: MIT
pragma solidity 0.8.16 ;
 contract arr
 {     uint256[] public n ;
       uint256 x = 0 ;

  function pl(uint256 a ) public
    {
      n[x] = a ;
      x++ ;
     }
 }

It is showing below error

Error showing image while calling function

It reads that

The transaction has been reverted to the initial state. Note: The called function should be payable if you send value and the value you send should be less than your current balance. Debug the transaction to get more information.

I am new to solidity. Can anyone please explain it to me that why = opearator is not working with arrays. I read that Solidity is similar to Javascript & in Jsp it is working fine ?