Angular:

http://angularjs.org/

by mrajcok

HTML

<div ng-controller="MyCtrl">
  <button validate-price="{priceValid: {'disabled': 'disabled'}}">Checkout</button>
</div>

JavaScript

var app = angular.module('myApp',[]);

app.directive('validatePrice', function($parse) {
    return {
        link: function(scope, el, attrs){
            var model = $parse(attrs.validatePrice);
            console.log(model(scope));
            console.log(scope.$eval(attrs.validatePrice));
            //console.log(attrs.validatePrice);
        }
    };
});

function MyCtrl($scope) {
    $scope.priceValid  = true;
}