Nested Object accessing without Maybe, maybe.

nestedObjects.js

const NOTHING = {};

const safeProperty = (obj, propertyName) => (obj[propertyName] ? obj[propertyName] : NOTHING);

const recurProperties = (obj, ...propertyNames) =>
  propertyNames.reduce(
    (accValue, currentProperty) =>
      accValue[currentProperty] ? accValue[currentProperty] : NOTHING,
    obj
  );

const ifPropertyThen = (fn, obj, ...propertyNames) =>
  recurProperties(obj, ...propertyNames) === NOTHING ? NOTHING : fn(obj);

describe("The safeProperty function", () => {
  it("should return NOTHING if the property doesn't exist", () => {
    const expected = NOTHING;
    const actual = safeProperty({}, "prop");
    expect(expected).toBe(actual);
  });

  it("should return the property if it exists", () => {
    const expected = "property";
    const actual = safeProperty({ prop: "property" }, "prop");
    expect(expected).toBe(actual);
  });
});

describe("The recurProperties function", () => {
  it("should return NOTHING if the first property doesn't exist", () => {
    const expected = NOTHING;
    const actual = recurProperties({}, "prop");
    expect(expected).toBe(actual);
  });

  it("should return NOTHING if the second property doesn't exist", () => {
    const expected = NOTHING;
    const actual = recurProperties({ prop: "notAnObject" }, "prop", "secondProp");
    expect(expected).toBe(actual);
  });

  it("should return return the second property if it exists", () => {
    const expected = "hello";
    const actual = recurProperties({ prop: { secondProp: "hello" } }, "prop", "secondProp");
    expect(expected).toBe(actual);
  });
});

describe("The ifPropertyThen function", () => {
  it("should return Nothing if the property doesn't exist", () => {
    const expected = NOTHING;
    const actual = ifPropertyThen(x => x, {}, "prop");
    expect(expected).toBe(actual);
  });

  it("should apply the function given to the object passed and return its result", () => {
    const expected = { prop: 2 };
    const actual = ifPropertyThen(
      x => {
        x.prop++;
        return x;
      },
      { prop: 1 },
      "prop"
    );
    expect(expected).toEqual(actual);
  });
});