Validate Numeric value with negative and decimals using Javascript

The below script shows how to validate a value to be Numeric or decimal with negative value. It will not allow the user to enter any other special characters.
Allows negative and non negative decimal values.

//Validate Numeric value (Allows negative  value)
//-------------------------------------------------
function allowNegativeNumber(e) {
    var charCode = (e.which) ? e.which : event.keyCode
    if (charCode > 31 && (charCode < 45 || charCode > 57) || charCode == 46) {
        return false;
    }
    return true;
}


//Validate Numeric value with negative and decimals 
//-------------------------------------------------
function allowNegativeDecimalNumber(e) {   
    var charCode = (e.which) ? e.which : event.keyCode
    if (charCode > 31 && (charCode < 45 || charCode > 57)) {
        return false;
    }
    return true;
}