NW | 25-ITP-Sep | TzeMing Ho | Sprint 2 |sprint-2-exercises #797

TzeMingHo · 2025-10-19T17:33:45Z

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

I have tried to create tests for the functions, according to the TPP principles, followed by refactoring the functions to make them work.

CameronDowner

This is looking really strong - I've asked some questions to test your understanding 🙂

Let me know if you have any questions

CameronDowner · 2025-10-21T20:55:54Z

Sprint-2/debug/address.js


+// I guess the bug could be related to how to access property in an object.
+// address[0] may not be able to access houseNumber as a key
+// if we change address[0] to address['houseNumber'] or address.houseNumber, it may resolve the problem.


Why would it not be able to access via address[0]?

address[0] can't access houseNumber because address is an object. When address[0] is read, it is looking for a key named 0 inside the address, which leads to "undefined" since the key 0 doesn't exist.

CameronDowner · 2025-10-21T20:57:49Z

Sprint-2/debug/author.js

-for (const value of author) {
-  console.log(value);
-}
+console.log(Object.values(author));


What if we wanted to console.log each property at a time?

If we wanted to print each property line by line, we could get the properties in an array by Object.keys(author), map each property, and print them out one by one.

Object.keys(author).map((key) => console.log(key));

CameronDowner · 2025-10-21T20:59:51Z

Sprint-2/debug/recipe.js

 console.log(`${recipe.title} serves ${recipe.serves}
  ingredients:
-${recipe}`);
+${recipe.ingredients.map((ingredient) => `${ingredient}`).join("\n")}`);


If we extract this value, is there a way we couple simplify this?

`${recipe.ingredients.map((ingredient) => `${ingredient}`).join("\n")}`;

Yeah. You are right. We can simplify this line to ${recipe.ingredients.join("\n")}, which can also print each ingredient on each line.

CameronDowner · 2025-10-21T21:01:44Z

Sprint-2/implement/lookup.js

@@ -1,5 +1,16 @@
-function createLookup() {
-  // implementation here
+function createLookup(arr) {


This is looking really good

CameronDowner · 2025-10-21T21:07:43Z

Sprint-2/interpret/invert.test.js

+describe("testing invert function", () => {
+  const errorMessage = "Input should be an object";
+  it("should throw error message when input is not an object", () => {
+    expect(() => invert("abc")).toThrow(errorMessage);


Why do we put this invert call inside an arrow function?

We put this invert function inside an arrow function because we expect it will fail with invalid data input. If the invert function is called as usual, like invert("abc"), the function will be fired up immediately. We don't have time to catch the error and compare it with an error message.
So, the () => arrow function is doing a referencing job, call the invert function when we expect it to fail.

CameronDowner · 2025-10-21T21:08:38Z

Sprint-2/interpret/invert.test.js

+      "[1]": "a",
+      "[2]": "b",
+    });
+    expect(invert({ a: { b: 1 }, c: { d: 2 } })).toStrictEqual({


What's the difference between toStrictEqual and toEqual used earlier in Sprint-2/implement/querystring.test.js?

toStrictEqual is stricter than toEqual. It will check the types of data, as we are testing undefined as a value, we should use toStrictEqual. Otherwise, the test will ignore undefined like toEqual does.

CameronDowner · 2025-10-21T21:10:03Z

Sprint-2/stretch/count-words.js

+  for (element of strArray) {
+    result[element] = (result[element] || 0) + 1;
+  }
+  return Object.fromEntries(Object.entries(result).sort((a, b) => b[1] - a[1]));


What's the benefit of .sort here?

The sort function can rearrange the words' order based on the frequency they appear. We use a desc sort to move the words that appear more to the top of the list.

Objects appear to keep the order we set - and in most cases they will - but technically JavaScript doesn’t guarantee that order (especially for number keys).

So while it looks sorted when you log it, you shouldn’t always rely on that

For this exercise though, it works perfectly 🙂

So, if we prefer order matters, we should choose an array for testing?

CameronDowner · 2025-10-21T21:11:58Z

Sprint-2/stretch/mode.js


+function calculateMode(list) {
+  // track frequency of each value
+  const frequencyArray = trackFrequency(list);


Is this an array if the trackFrequency function returns a Map?

Actually not. I didn't know it before. A map is actually an object map, but it works like an array because it has a built-in iterator to loop through the map.
If we wanted to convert the frequency map into an array, we could [...frequency.entries()] or Array.from(frequency.entries())

You're right - in this case Map behaves like an object but has an iterator - so it has an order to the elements

CameronDowner · 2025-10-22T20:32:51Z

@TzeMingHo Changes are looking good 🙂

Could you also answer the questions I've asked in the comments? Not problem if you don't know all the answers, but would be good to see what you think

TzeMingHo · 2025-10-22T21:24:49Z

@TzeMingHo Changes are looking good 🙂

Could you also answer the questions I've asked in the comments? Not problem if you don't know all the answers, but would be good to see what you think

Sorry to get back to you late. I forgot to submit my replies. So you couldn't see them yet.

CameronDowner · 2025-10-22T21:35:46Z

@TzeMingHo Changes are looking good 🙂
Could you also answer the questions I've asked in the comments? Not problem if you don't know all the answers, but would be good to see what you think

Sorry to get back to you late. I forgot to submit my replies. So you couldn't see them yet.

No problem 🙂 Easily done - all looking really good!

TzeMingHo added 12 commits October 13, 2025 16:21

fixed bug in address.js

b8e5f68

getting all the values in object author

bfe0b62

fixed bug in recipe

de5e07a

completed contains tests and function

6124343

completed lookup

9eaf9c8

updated test in lookup

d91f6e7

added cases for querystring test and refactored the function

5f097e4

added edge cases for tally and refactored its function

8fa0a48

completed invert tests and its function

3758f52

completed count-word tests and function

5c349f2

refactored mode's function

cd89aa1

completed till tests and function

4a4cd94

TzeMingHo added 📅 Sprint 2 Assigned during Sprint 2 of this module Needs Review Trainee to add when requesting review. PRs without this label will not be reviewed. labels Oct 19, 2025

CameronDowner reviewed Oct 21, 2025

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CameronDowner added Reviewed Volunteer to add when completing a review with trainee action still to take. and removed Needs Review Trainee to add when requesting review. PRs without this label will not be reviewed. labels Oct 21, 2025

TzeMingHo added 2 commits October 22, 2025 11:39

simplify ingredients printing

d5a16f5

updated to frequency map not an array

5f76350

TzeMingHo added Needs Review Trainee to add when requesting review. PRs without this label will not be reviewed. and removed Reviewed Volunteer to add when completing a review with trainee action still to take. labels Oct 22, 2025

CameronDowner added Reviewed Volunteer to add when completing a review with trainee action still to take. and removed Needs Review Trainee to add when requesting review. PRs without this label will not be reviewed. labels Oct 22, 2025

TzeMingHo added Needs Review Trainee to add when requesting review. PRs without this label will not be reviewed. and removed Reviewed Volunteer to add when completing a review with trainee action still to take. labels Oct 22, 2025

CameronDowner added Complete Volunteer to add when work is complete and all review comments have been addressed. and removed Needs Review Trainee to add when requesting review. PRs without this label will not be reviewed. labels Oct 22, 2025

TzeMingHo mentioned this pull request Nov 2, 2025

NW | 25-ITP-Sep | Data groups | TzeMing Ho TzeMingHo/My-Coursework-Planner#40

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NW | 25-ITP-Sep | TzeMing Ho | Sprint 2 |sprint-2-exercises #797

NW | 25-ITP-Sep | TzeMing Ho | Sprint 2 |sprint-2-exercises #797

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TzeMingHo commented Oct 19, 2025

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CameronDowner Oct 21, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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CameronDowner commented Oct 22, 2025

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TzeMingHo commented Oct 22, 2025

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CameronDowner commented Oct 22, 2025

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