[MixPetrov]

Пробовал так:

function isright(product_id, maximum) {
	var ns = +($('input[name=\'' + product_id + '\']').val().replace(/\D/g,''))||0;
	if (ns>maximum)	ns=maximum;	
        //if (ns<10)  ns=10;
	$('input[name=\'' + product_id + '\']').val(ns) }

Так:

function isright(product_id, maximum) {
	var ns = +($('input[name=\'' + product_id + '\']').val().replace(/\D/g,''))||0;
	var ms = $('input[name=\'' + product_id + '\']').val(maximum);
	if (ns>ms)	ns=ms;	
        //if (ns<10)  ns=10;
	$('input[name=\'' + product_id + '\']').val(ns) }

Так:

function isright(product_id, maximum) {
	var ns = +($('input[name=\'' + product_id + '\']').val().replace(/\D/g,''))||0;
	if (ns>$('input[name=\'' + product_id + '\']').val(maximum);)	ns=$('input[name=\'' + product_id + '\']').val(maximum);;	
        //if (ns<10)  ns=10;
	$('input[name=\'' + product_id + '\']').val(ns) }

Не получилось