test.js

(function() {

  function Foo() {
    this.bigData = new Array(5000000).join("XXXXX");
    this.smallData = "bla bla";
  }

  Foo.prototype.m = function() {
    var smallData = this.smallData;
    $(window).on('click', function() {
      console.log(smallData);
    });
  };

  window.f = new Foo();
  window.f.m();
  delete window.f;
}());

// VS

(function() {

  function Bar() {
    var bigData = new Array(5000000).join("XXXXX");
    var smallData = "bla bla";
    return {
      m: function() {
        $(window).on('click', function() {
          console.log(smallData);
        });
      }
    };
  }

  window.b = new Bar();
  window.b.m();
  delete window.b;
}());

// VS

(function() {

  function Bar() {
    var bigData = new Array(5000000).join("XXXXX");
    var smallData = "bla bla";
    return {
      m: function() {
        $(window).on('click', function() {
          console.log(smallData);
          bigData += "X";
        });
      }
    };
  }

  window.b = new Bar();
  window.b.m();
  delete window.b;
}());

// VS

(function() {

  function Bar() {
    var bigData = new Array(5000000).join("XXXXX");
    var smallData = "bla bla";
    return {
      m: function() {
        $(window).on('click', function() {
          console.log(smallData);
        });
      },
      n: function() {
        bigData += "X";
      }
    };
  }

  window.b = new Bar();
  window.b.m();
  delete window.b;
}());