这样子吧.~ <script type="text/javascript"> while(true) { var p = prompt("请输入偶数",".."); if(p%2==0&&!isNaN(p)) break; } var flag = false; var a = parseInt(p); for(var i=1;i<=a;i++) { var j; if(i%2!=0) { j=a-i; document.write(i,j); document.write("<br/>"); } } </script>