HTML 的 form 提交之前如何验证数值文本框的内容全部为数字? 否则的话提示用户并终止提交?

实现代码如下：

<form onsubmit=’return chkForm(this)’>

<input type="text" name="d1"/>

<input type="submit"/>

</form>

<script type=”text/javascript” />   

function chkForm(this)

       {

              varvalue = thist.d1.value;

              varlen = value.length;

              for(vari=0;i<len;i++)

              {

                     if(value.charAt(i)>"9"|| value.charAt(i)<"0")

                     {

                            alert("含有非数字字符");

                            returnfalse;

                     }

              }

              returntrue;

       }

</script>