javascript checking empty asp.net textboxt using button
<p>so i want to check if the textbox filled or no when i click submit button</p>

<p>and so far i only have this script on my mind, btw i'm new at javascript, here is my code :</p>

<pre><code>  function checkTextField(field) {
        if (field.value == '') {
            alert("Field is empty");
        }
    }

&lt;asp:TextBox ID="txtPOno" runat="server"&gt;&lt;/asp:TextBox&gt;
&lt;asp:TextBox ID="txtShipto" runat="server"&gt;&lt;/asp:TextBox&gt;
&lt;input type="text"  id="txtRRDate" name="txtRRDate"&gt;
&lt;asp:Button ID="btnSubmit" runat="server"&gt;&lt;/asp:TextBox&gt;
</code></pre>