dig_challenge.ts

import { expect } from "chai";

function dig(obj: any, key: string): any {
  return key.split(".").reduce((memo, keyPiece) => {
    if (!Object.keys(memo).includes(keyPiece)) {
      throw new Error("key not found");
    }
    return memo[keyPiece];
  }, obj);
}

describe("dig", () => {
  let obj: any;
  beforeEach(() => {
    obj = {
      a: 1,
      b: {
        c: 2,
        d: {
          e: 3,
          f: {
            g: 4,
          },
        },
      },
    };
  });

  it("returns the result of a single key", () => {
    expect(dig(obj, "a")).to.equal(obj.a);
  });
  it("returns the value of a nested key", () => {
    expect(dig(obj, "b.d")).to.equal(obj.b.d);
  });
  it("returns the value of a very nested key", () => {
    expect(dig(obj, "b.d.f.g")).to.equal(obj.b.d.f.g);
  });

  it('throws "key not found" if the key is empty', () => {
    expect(() => {
      dig(obj, "");
    }).to.throw("key not found");
  });
  it('throws "key not found" if single key fails to match', () => {
    expect(() => {
      dig(obj, "z");
    }).to.throw("key not found");
  });
  it('throws "key not found" if nests key fails to match', () => {
    expect(() => {
      dig(obj, "b.d.z");
    }).to.throw("key not found");
  });
});

results.txt

  dig
    ✓ returns the result of a single key
    ✓ returns the value of a nested key
    ✓ returns the value of a very nested key
    ✓ throws "key not found" if the key is empty
    ✓ throws "key not found" if single key fails to match
    ✓ throws "key not found" if nests key fails to match