Only Numeric with Single Decimal - JavaScript

//Keypress event on a Class
$('.onlyNumeric').on('keypress', function(e) {
return isNumber(event, this);
   });

//Function to validate Number, Decimal and Negative sign
function isNumber(evt, element) {
        var charCode = (evt.which) ? evt.which : event.keyCode

        if (
            (charCode != 46 || $(element).val().indexOf('.') != -1) &&  
            (charCode < 48 || charCode > 57))
            return false;

        return true;
    }