London | 26-ITP-May | Vito Moratti | Sprint 1 | Module data groups/sprint1 by vmoratti · Pull Request #1297 · CodeYourFuture/Module-Data-Groups

vmoratti · 2026-07-26T16:24:55Z

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

Completed exercises for Sprint 1 except for stretch, which i didn't have time for.

Questions

Stretch is optional right?

cjyuan · 2026-07-31T16:07:10Z

+  if (!Array.isArray(list) || list.length < 2) {
+    return null;
+  }


Why can't an array containing one number have a median?

cjyuan · 2026-07-31T16:09:41Z

+    let newArr = [];
+  for (let i = 0; i < arr.length; i++) {


Indentation is off.

Have you installed the prettier VSCode extension and enabled "Format on save/paste" on VSCode,
as recommended in
https://github.com/CodeYourFuture/Module-Structuring-and-Testing-Data/blob/main/readme.md
?

I have that installed, sorry, I don't know what happened there.

cjyuan · 2026-07-31T16:10:39Z

+test("given an array with no duplicates, it returns a copy of the original array", () => {
+  expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+});


Your function implementation is correct. However, this test could be improved to better ensure
that any future changes continue to align with the expected behavior described on line 25:

Then it should return a copy of the original array

This test should fail if the function returns the original array (instead of a copy of the original array).

The current test checks only if both the original array and the returned array contain identical elements.
In order to validate the returned array is a different array, we need an additional check.

Can you find out what this additional check is?

cjyuan · 2026-07-31T16:14:05Z

+        const filteredList = elements.filter((value) => typeof value === "number");
+        return Math.max( ...filteredList)}


Could the code on line 5-6 works also when elments.length < 1?

What do you expect from the function calls findMax([0, NaN, 1])? Does your function return the value you expected?

cjyuan · 2026-07-31T16:16:07Z

+test("given an array with only non-number values, returns -Infinity", () => {
+  expect(findMax(["apple", null, undefined])).toEqual(-Infinity);
+  expect(findMax([null, undefined])).toEqual(-Infinity);
+  expect(findMax(["apple", "banana"])).toEqual(-Infinity);
+});


When a string representing a valid numeric literal (for example, "300") is compared to a number,
JavaScript first converts the string into its numeric equivalent before performing the comparison.
As a result, the expression 20 < "300" evaluates to true.

To test if the function can correctly ignore non-numeric values,
consider including a string such as "300" in the relevant test cases.

cjyuan · 2026-07-31T16:16:38Z

@@ -1,4 +1,10 @@
 function sum(elements) {
+    let innit = 0;


What does the name innit mean?

cjyuan · 2026-07-31T16:17:08Z

@@ -1,4 +1,10 @@
 function sum(elements) {
+    let innit = 0;
+    const filteredList = elements.filter((value) => typeof value === "number");


What do you expect from the following function calls (on extreme cases)?
Does your function return the value you expected?

sum([NaN, 1]); sum([Infinity, -Infinity]);

cjyuan · 2026-07-31T16:17:27Z

+return innit; 
 }


Indentation is off.

cjyuan · 2026-07-31T16:17:55Z

+test("given an array with decimal/float numbers, returns the correct total sum", () => {
+  expect(sum([1.5, 2.5, 3.5])).toEqual(7.5);
+  expect(sum([-1.5, -2.5, -3.5])).toEqual(-7.5);
+});


Decimal numbers in most programming languages (including JS) are internally represented in "floating point number" format. Floating point arithmetic is not exact. For example, the result of 46.5678 - 46 === 0.5678 is false because 46.5678 - 46 only yield a value that is very close to 0.5678. Even changing the order in which the program add/subtract numbers can yield different values.

So the following could happen

expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.805 ); // This fail expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.8049999999999997 ); // This pass expect( 0.005 + 0.6 + 1.2 ).toEqual( 1.8049999999999997 ); // This fail console.log(1.2 + 0.6 + 0.005 == 1.805); // false console.log(1.2 + 0.6 + 0.005 == 0.005 + 0.6 + 1.2); // false

Can you find a more appropriate way to test a value (that involves decimal number calculations) for equality?

Suggestion: Look up

Checking equality in floating point arithmetic in JavaScript

Checking equality in floating point arithmetic with Jest

cjyuan · 2026-07-31T16:20:25Z

+  for (let i of list) {
+    if (i === target) {


The identifier i is normally used to represent an array index. Could you rename it?

Update median calculation to handle empty arrays.

vmoratti added 16 commits July 24, 2026 16:19

rewrite function

cae4a14

write function and create two tests

f9211a3

change function, write some tests

183be23

write test for decimal numbers

8e59e19

write test for mixed array of numbers and non-numbers

f9080a3

write test for mixed array of non-numbers

72267a0

add empty array test

4f2f012

write sum function

f48b3b9

add tests for negative and decimal numbers

4fe95d9

write test for mixed array

120a279

add validation to the function

a02f092

add test with non-number array

a22313c

add tests for an empty, and array wwith duplicates

dc82a68

write function

4522a37

add test with duplicates

c22b7f9

refactor includes function

8f921db

vmoratti added the Needs Review Trainee to add when requesting review. PRs without this label will not be reviewed. label Jul 26, 2026

cjyuan reviewed Jul 31, 2026

View reviewed changes

cjyuan 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 Jul 31, 2026

vmoratti added 2 commits July 31, 2026 17:29

Fix median function to allow single element lists

0bfabe2

Update median calculation to handle empty arrays.

Fix indentation in dedupe function

23d816f

		const filteredList = elements.filter((value) => typeof value === "number");
		return Math.max( ...filteredList)}

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vmoratti commented Jul 26, 2026

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