jQuery Input Field Incrementer

jquery.increment.js

(function (jQuery) {

    jQuery.fn.extend({
        incrementButtons:function (options) {

            var defaults = {
                minVal:null,
                maxVal:null,
                incClass:'inc',
                decClass:'dec',
                callback: function(value){}
            }

            var getNumVal = function (element) {//get numeric value of an object
                var value = Number(element.val());
                return isNaN(value) ? 0 : value;
            }

            var correctValue = function (min, max, value) {
                var checkMin = min != null && !isNaN(0 + min);
                var checkMax = max != null && !isNaN(0 + max);
                if (value > max && checkMax) {
                    return max;
                }
                if (value < min && checkMin) {
                    return min;
                }
                return value;
            }

            var options = jQuery.extend(defaults, options);

            return this.each(function () {
                var obj = jQuery(this);

                // Wrap obj:
                obj.wrap('<div class="increment"></div>');
                
                // Create buttons:
                var decButton = obj.after('<a href="#" class="' + options.decClass + '">-</a>').next();
                var incButton = obj.after('<a href="#" class="' + options.incClass + '">+</a>').next();

                // Focus value:
                var focusValue;

                incButton.click(function (e) {
                    e.preventDefault();
                    obj.val(correctValue(options.minVal, options.maxVal, (getNumVal(obj) + 1)));
                    options.callback(getNumVal(obj));
                });
                decButton.click(function (e) {
                    e.preventDefault();
                    obj.val(correctValue(options.minVal, options.maxVal, (getNumVal(obj) - 1)));
                    options.callback(getNumVal(obj));
                });
                obj.focus(function () {
                    focusValue = obj.val();
                });
                obj.blur(function () {                    
                    obj.val(correctValue(options.minVal, options.maxVal, getNumVal(obj)));
                    if(obj.val() != focusValue)
                    {
                        options.callback(getNumVal(obj));
                    }
                });
            });
        }
    });

})(jQuery);