<head>chess</head> <body> <script> let lineSize = +prompt("Enter size of table line "); let str = ""; for (let i = 0; i < lineSize; i++) { for (let j = 0; j < lineSize; j++) { str += ((j+i)% 2) == 0 ? "." : "#"; } str += '\n'; } alert(str); </script> </body>
