jquery 必填项判断表单是否为空的方法

<form onsubmit="if(confirm(确定好你所填写的正确，不然会发错!)) {return checkForm();}else{return false;}" >
<table >
<tr>
<td>选择发送人<font class="red">*</font></td>
<td>
<input type="text" name="sendto_type[]" id="sendto_type1" value="1" >按城市发送

</td>
</tr>

<tr>
<td>选择发送人2<font class="red">*</font></td>
<td>
<input type="text" name="sendto_type[]" id="sendto_type1" value="1" >按城市发送
</td>
</tr>
</table>
</form>

<script>
function checkForm() {
pass = true;
$("td:contains(*)").next().find("input").each(function(){
if(this.value == ) {
text = $(this).parent().prev().text();
alert(text+"是必填项");
this.focus();
pass = false;
return false;//跳出each
}
});
return pass;
}
</script>