多重提交表单的校验方法

<script language="JavaScript"><!--
document.returnValue=true;//一个全局变量，给初值。
function validateForm() { var errors;errors=&#39;&#39;;if (document.PostTopic.title.value=="")errors="标题不能为空";if( document.PostTopic.intro.value.length>10)errors+="\n简介不能多于10个字";if (errors!=&#39;&#39;) alert(errors);document.returnValue = (errors == &#39;&#39;);}
file://--></script>
<FORM ACTION="" METHOD="post" NAME="PostTopic" onSubmit="return document.returnValue;"><input type=text name=title value=""><input type=text name=intro value=""><INPUT TYPE="submit" NAME=Submit VALUE="新增" class=buttonface onclick="document.PostTopic.action=&#39;addone.php&#39;;validateForm(); return document.returnValue;"><INPUT TYPE="RESET" NAME=Reset VALUE="重置" class=buttonface ><INPUT TYPE="submit" NAME="Submit" VALUE="修改" class=buttonface onclick="document.PostTopic.action=&#39;modify.php&#39;;validateForm(); return document.returnValue;"></FORM>