Работи си!

function solve(number) {
  if (typeof number === 'number') {
    for (let i = 0; i < number; i++) {
      let array = [];
      for (let i = 0; i < number; i++) {
        array[i] = '*';
      }

      let result = array.join(' ');
      console.log(result);
    }
  } else {
    for (let i = 0; i < 5; i++) {
      let array = [];
      for (let i = 0; i < 5; i++) {
        array[i] = '*';
      }

      let result = array.join(' ');
      console.log(result);
    }
  }
}