Question

Is it possible say a person enters an integer value 5 in a Textbox and automaticall a .00 is added in the end say 5.00

<asp:TextBox ID="txtAmountTransfer" runat="server" Width="55%" CssClass="right"></asp:TextBox>

Answer 1

@CR41G14 is correct. .toFixed(2) is all you need.

As far as where and how, I would recommend using the change event on the input box as it is the least intrusive for the user. (The blur event would also not be unreasonable)

Since the value of the text field will be a string you will need to parse it as @Snuffleupagus points out. In your case, I would recommend parseFloat because then your field could potentially handle the user entering 5.2 which could become 5.20. (using parseInt you would end up with 5.00).

One additional note is recognizing that if the user types non-numeric characters (or really any value that will not parse) into the field, it will result in a display of NaN, which actually seems fairly reasonable in your case.

Using jQuery:

$('#txtAmountTransfer').change(function(){
    $(this).val(parseFloat($(this).val()).toFixed(2))
});

Similar example using native code:

var textField = document.getElementById('txtAmountTransfer');
    textField.onchange = function(){
        this.value = parseFloat(this.value).toFixed(2);     
    }