Creating chains in js

chains.js

function Test(){
  this.x = "I'm x";
  this.publicFn = function(){
    console.log("I'm a instance method");
  }
}

Test.prototype = {
  protoFn : function(){
    console.log("And I'm a proto function");
    return this;
  }
}

var z = new Test();
z.protoFn().publicFn();