[рони]

Tanya51,
может так?

function createCounter(){
var Count = 1;
createCounter.prototype.inc = function () {
           Count++;
              };
createCounter.prototype.dec = function () {
           Count--;
              };
createCounter.prototype.getValue = function () {
           return Count
              };

}

var counter = new createCounter();
counter.inc();
counter.inc();
counter.inc();
counter.dec();
alert( counter.getValue() );