var intRegex = /^d+$/;
var floatRegex = /^((d+(.d *)?)|((d*.)?d+))$/;

var str = $('#myTextBox').val();
if(intRegex.test(str) || floatRegex.test(str)) {
   alert('I am a number');
   ...
}

var numberRegex = /^[+-]?d+(.d+)?([eE][+-]?d+)?$/;
var str = $('#myTextBox').val();
if(numberRegex.test(str)) {
   alert('I am a number');
   ...
}

isNaN(123)           // false
isNaN(-1.23)         // false
isNaN(5-2)           // false
isNaN(0)             // false
isNaN("100")         // false
isNaN("Hello")       // true
isNaN("2005/12/12")  // true

if (isNaN( $("#whatever").val() )) {
    // It isn't a number
} else {
    // It is a number
}

/^d+$/.match(value)
Number(value) == value

$("form").validate({
            errorElement: "div",
            errorClass: "error-highlight",
            onblur: true,
            onsubmit: true,
            focusInvalid: true,
            rules:{
                'nrInput': {
                    number: true,
                    required: true
                }
            });