Here are couple different ways

if (typeof FFX == "undefined") {
    FFX = {};
}

//Static class
FFX.Util = ({
     return {
      method:function(){
      }
})();
     
FFX.Util.method(); 
     


//Instance class
FFX.Util2 = ({
    // private method
    var methodA=function(){
      alert("Hello");
    };
     return {
      method:function(){
      //Call private method
        methodA();
      }
});
var x=FFX.Util();
x.method(); 

 

Another way

function MyClass(){
}

/* privileged functions */
MyClass.prototype.hello = function(){
    alert("Hello");
}   

Also you could see how jquery, prototype and alike handle classes and see if thats fits you needs.

Here are couple different ways

if (typeof FFX == "undefined") {
    FFX = {};
}

//Static class
FFX.Util = ({
     return {
      method:function(){
      }
})();
     
FFX.Util.method(); 
     


//Instance class
FFX.Util2 = ({
    // private method
    var methodA=function(){
      alert("Hello");
    };
     return {
      method:function(){
      //Call private method
        methodA();
      }
});
var x= new FFX.Util();
x.method(); 

 

Another way

function MyClass(){
}

/* privileged functions */
MyClass.prototype.hello = function(){
    alert("Hello");
}   

Also you could see how jquery, prototype and alike handle classes and see if thats fits you needs.