Validation Number and Decimal value asp.net

Validation Number and Decimal value asp.net
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 <script type="text/javascript">
        function onlyDotsAndNumbers(txt, event) {
            try {
                var charCode = (event.which) ? event.which : event.keyCode
                if (charCode == 46) {
                    if (txt.value.indexOf(".") < 0)
                        return true;
                    else
                        return false;
                }
                //backspace = 8, delete = 46, left arrow = 37,  right arrow = 39, tab=9
                if (charCode == 46 || charCode == 8 || charCode == 37 || charCode == 39 || charCode == 9) {
                    return true;
                }
                if (txt.value.indexOf(".") > 0) {
                    var txtlen = txt.value.length;
                    var dotpos = txt.value.indexOf(".");
                    if ((txtlen - dotpos) > 2)
                        return false;
                }
                if (charCode > 31 && (charCode < 48 || charCode > 57))
                    return false;
                return true;
            }
            catch (err) {
                alert('An error has occurred:' + err.message);
            }
        }
    </script>


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Calculate gridview textbox amount
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        function readEarning() {
            try {
                var totEarningAmount = 0;
                var EType = document.getElementById('<%=hfEType.ClientID %>').value;
                var DType = document.getElementById('<%=hfDType.ClientID %>').value; 

                //Employee Type Permanet and Deposit Type Bank
                if (EType == 1 && DType == 1) {
                    var gridEarning = document.getElementById('<%=gv_ESEearning.ClientID %>');
                    if (gridEarning.rows.length > 0) {
                        var inputs = gridEarning.getElementsByTagName("input");
                        for (var i = 0; i < inputs.length - 1; i++) {
                            if (inputs[i].name.indexOf("txtEarningAmount") > 1) {
                                if (inputs[i].value != "") {
                                    totEarningAmount = parseFloat(totEarningAmount) + parseInt(inputs[i].value);
                                }
                            }
                        }
                    }
                    document.getElementById('ContentPlaceHolder1_gv_Employee_Salary_earning_txtEarningAmount_5').value = totEarningAmount.toFixed(2);
                }
}
catch (err) {
                alert('An error has occurred:' + err.message);
            }
        }

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Gridview Textbox Fous and readonly
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document.getElementById('ContentPlaceHolder1_gvESearning_txtEarningAmount_0').setAttribute("readonly", "true");
                    document.getElementById('ContentPlaceHolder1_gvESearning_txtEarningAmount_0').focus();