$._formatGrid = (grid) => {
  return `\n${grid.map((row) => row.join("")).join("\n")}`;
};

const grid = [];
const size = 16;
for (let r = 0; r < size; r++) {
  const row = [];
  for (let c = 0; c < size; c++) {
    if (r === 0 || r === size - 1) row.push(".");
    else if (r < size / 2 && c === r + size / 4) row.push(".");
    else if (r >= size / 2 && c === r - size / 4) row.push(".");
    else if (r === size / 2 && c > size / 4 && c <= (3 * size) / 4)
      row.push(".");
    else if (Math.floor(Math.random() * 100) % 100 === 0) row.push("*");
    else row.push(" ");
  }
  grid.push(row);
}
const pic = $._formatGrid(grid);
return pic;

Output

................
     .          
      .         
       .        
        .       
         .      
          .     
           .    
    .........   
     .          
      .         
       .        
        .       
         .**    
          .     
................