read-only proxy

readonly-proxy.js

function wrap(aObject)
{
  if (aObject === undefined || aObject === null) {
    return aObject;
  }
  let type = typeof(aObject);
  if (type == "string" || type == "number" || type == "boolean" || type == "function") {
    return aObject;
  }

  let getOwnPropertyDescriptor = function (aObject, name) {
    var desc = Object.getOwnPropertyDescriptor(aObject, name);
    if (desc === undefined) {
        return undefined;
    }
    if ("value" in desc) {
      desc.value = wrap(desc.value);
      desc.writable = false;
    } else {
      desc.getter = wrap(desc.getter);
      desc.setter = null;
    }
    return desc;
  };
  let getPropertyDescriptor = function (aObject, name) {
    let desc;
    while (aObject && undefined === (desc = getOwnPropertyDescriptor(aObject, name))) {
      aObject = Object.getPrototypeOf(aObject);
    }
    return desc;
  };

  return Proxy.create({
    getOwnPropertyDescriptor: function (name) {
      return getOwnPropertyDescriptor(aObject, name);
    },
    getPropertyDescriptor: function (name) {
      return getPropertyDescriptor(aObject, name);
    }
  }, wrap(Object.getPrototypeOf(aObject)));
}