脚本语言练习累加求和 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>

<body>
</body>
</html>
<script>
var a=prompt("请输入一个整数","只能是整数");
if(a!=null)
{
    var b=isNaN(a);
    if(b==false)
    {
        var c=parseInt(a);
        var sum=0;
        for(var i=1;i<=c;i++)
        {
            sum+=i;
        }
        alert(sum);
    }
    else
    {
        alert("输入有误！");
    }
}
else
{
}



</script>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>

<body>
请输入一个数字:<input type="text"  id="text"/>&nbsp;&nbsp;&nbsp;<input  type="button" value="请点击" onclick="add()"/>

</body>
</html>
<script>
function add()
{
  var a= document.getElementById("text");
  var b=isNaN(a.value);
  if(b==false)
  {
      var c= parseInt(a.value);
      var sum=0;
      for(var i=0;i<=c;i++)
      {
          sum+=i;
      }
      document.write(sum);
 }
 else
  {
      alert("输入有误！");
  }
}

</script>

 

posted @ 2016-05-23 20:20  枫炎  阅读(351)  评论(0)    收藏  举报