while文でselectボタンを作る <select><script>var i = 2;while( i <= 20 ) { document.write('<option value="i">'+i+'個</option>'); i += 2;}</script></select> 結果 for文でselectボタンを作る <select><script>for(var i = 2; i <= 20; i+=2){ document.write('<option value="i">'+i+'個</option>');}</script></select> 結…