Allow only numbers in textbox using javascript

Use the following code:

function AllowNumsOnly(evt)
{
    var charCode = (evt.which) ? evt.which : event.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
        document.getElementById('spnError').innerHTML = 'Allows only numbers';
        return false;
    }
    else {
        document.getElementById('spnError').innerHTML = '';
        return true;
    }
}

<style>
    #spnError {color:Red;font-size:11px;}
</style>

<asp:TextBox ID="txt_Qty" runat="server" onkeypress="return AllowNumsOnly(event);"></asp:TextBox><span id="spnError"></span>

Tag: Allow only numbers in textbox using javascript,allow numbers only onkeypress