Birmingham | ITP Jan 2026 | Arunkumar Akilan | Sprint 2 | Data Groups

[arunkumarakilan]

Learners, PR Template

Self checklist

• I have titled my PR with Region | Cohort | FirstName LastName | Sprint | Assignment Title
• My changes meet the requirements of the task
• I have tested my changes
• My changes follow the style guide

---

Changelist

🐞 Debug

• Fixed bugs in address.js
• Fixed bugs in author.js
• Fixed bugs in recipe.js
• Ensured all debug tests pass

⚙️ Implementation

• Implemented tally function to count occurrences in an array
• Implemented contains function to check if object has a property
• Implemented createLookup function to convert key-value pairs into an object
• Implemented parseQueryString with edge case handling
• Implemented invert function to swap keys and values

🧪 Testing

• Added unit tests for all functions
• Covered edge cases (empty input, invalid input, multiple values, etc.)
• All tests are passing

---

Notes

• Used methods like Object.keys, Object.entries, and array iteration
• Improved understanding of objects and key-value handling

---

Questions

No questions at the moment

[cjyuan]

Can you ensure all the code is consistently formatted?
If you had successfully enabled "Format on save" and specified "Prettier" as your default JS formatter, you would not have this issue.

[cjyuan]

Array is also an object where it indexes are its keys.
Object.hasOwn([1, 2, 3], "a") evaluates to false because "a" is not a key (index) of the array.
However, Object.hasOwn([1, 2, 3], "0") evaluates to true because "0" is a key (index) of the array.

To test if the implemented function can correctly return false when the first argument is an array,
we should specify an actual key of the array.

[arunkumarakilan]

Thanks for the clarification!

I understand that arrays are objects and that
Object.hasOwn([1, 2, 3], "0") returns true because "0" is a valid index.

However, in my implementation I explicitly treat arrays as invalid inputs:

if (typeof object !== "object" || Array.isArray(object) || object === null)

So the function throws an error before reaching Object.keys().
That’s why the test passes — it never evaluates array indexes like "0".

I’ll update either the test or the implementation depending on the expected behaviour

[cjyuan]

It's not about your function, it is correctly implemented.

In practice, we prepare tests not just to check our implementation, but also to serve as a guard for future modification. In TDD, the tests will also serve as the spec that define how the function should be implemented.
That's why I keep emphasising the importance of preparing the tests correctly.

[cjyuan]

Changes look good.