Protect JS object properties

protector.js

  const HasProtectedAccessor = stampit({
    // stamp configuration
    deepConf: {
      // collect all the property names to protect
      protectedProperties: {}
    },
    statics: {
      // API of the stamp
      protectProperty(names) {
        // will deep merge the base objects with `names`
        return this.deepConf({ protectedProperties: names });
      }
    },
    init(keyValueMap, { stamp }) {
      // The properties to protect
      let { protectedProperties } = stamp.compose.deepConfiguration || {};
      // The closured map of protector functions
      const protectors = new Map(Object.entries(protectedProperties)
        .filter(([key, value]) => typeof value === "function"));
      // The closured map of protected values
      const map = new Map();
      for (const key of protectors.keys()) map.set(key, undefined);

      for (const name of map.keys()) {
        // Using JS getters and setters to protect properties
        Object.defineProperty(this, name, {
          get () { return map.get(name); },
          set (value) {
            if (protectors.get(name)(value, name))
              map.set(name, value);
          }
        });
      }

      // Initialise this object instance with the configured values
      for (const [key, value] of Object.entries(keyValueMap)) {
        if (map.has(key)) this[key] = value;
      }
    }
  });

  const _ = require("lodash");
  const TestAccessors = stampit(
    HasProtectedAccessor.protectProperty({
      fullName: v => v === undefined || _.isString(v),
      address: _.isArray,
    }),
    { name: "TestAccessors" }
  );

  const instance1 = TestAccessors({ fullName: "John Johnson", address: [] });
  t.strictEqual(instance1.fullName, "John Johnson");
  t.deepEqual(instance1.address, []);

  const instance2 = TestAccessors({ fullName: ["array"], address: "oops" }); // WILL NOT SET
  t.strictEqual(instance2.fullName, undefined);
  t.strictEqual(instance2.address, undefined);

  instance2.fullName = function () {}; // WILL NOT SET
  t.strictEqual(instance2.fullName, undefined);
  instance2.address = { NotAnArray: 111 }; // WILL NOT SET
  t.strictEqual(instance2.address, undefined);

  instance2.fullName = "Andrew Anderson";
  t.strictEqual(instance2.fullName, "Andrew Anderson");
  instance2.address = ["111 Acme St", "London"];
  t.deepEqual(instance2.address, ["111 Acme St", "London"]);

  instance2.fullName = undefined;
  t.strictEqual(instance2.fullName, undefined);
  instance2.address = undefined; // WILL NOT SET
  t.deepEqual(instance2.address, ["111 Acme St", "London"]);