Question

The below code to validate TextBox is working fine onkeypress but when I use backspace to reduce the text length this code is unable to return back to the RED color. How to change color back to red on using backspace to reduce string length.

<script type="text/javascript">

    function limitlength(obj, length) {
        var maxlength = length
        if (obj.value.length > maxlength) {
            document.getElementById("TextBox1").style.backgroundColor = "green";
        }
        else
        {
            document.getElementById("TextBox1").style.backgroundColor = "red";
        }

    }

</script>

Enter text (max length is 5 characters):
<form id="form1" runat="server">
<br />
<br />
<asp:TextBox ID="TextBox1" onkeypress="return limitlength(this, 5)" runat="server"></asp:TextBox>
<br />
<br />
</form>

Answer 1

Either use onchange or onkeyup.
I think it’s better if you use onkeyup