This is a quick write up using underscore to create getters from a JSON object. A good use case is when the object is a response from an endpoint.

defineGetters.js

function defineGetters (context, obj) {
  this.get = {};

  // we iterate over the object via underscore creating getter functions
  _.each(obj, function (val, ind, list) {
    this.get[ind] = function() {
      return ( !_.isObject(val) || _.isArray(val) ? val : $.extend({}, val, true) );
    };
  }, this);
}


function Item (obj) {
  defineGetters(this, obj);
}

var item = new Item({foo: "bar", baz: {fred: "frodo"}});

var temp = item.get.baz();
// => {fred: "frodo"}

temp.fred = "messed up object";

item.get.baz();
// => {fred: "frodo"}

See also: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects#Defining_getters_and_setters