London | 26-ITP-Jan | Angela McLeary | Sprint 1 | Sprint 1 by AngelaMcLeary · Pull Request #1129 · CodeYourFuture/Module-Data-Groups

AngelaMcLeary · 2026-03-28T14:49:18Z

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Changelist

This PR is about fixing median.js, Implementing dedupe.js, max.js, sum.js and refactoring include.js.

cjyuan · 2026-03-31T17:25:00Z

Sprint-1/fix/median.js

-
+  if (!Array.isArray(list) || list.length === 0) return null;
+  //If the items are not an array or if the array is empty return null
+  const numbers = list.filter((num) => typeof num === "number");


Do you plan to consider also -Infinity, Infinity, and NaN in the median calculation (and in the functions in implement/max.js and implement/sum.js)?

cjyuan · 2026-03-31T17:26:05Z

Sprint-1/fix/median.js

+  const numbers = list.filter((num) => typeof num === "number");
+  if (numbers.length === 0) return null;
+  //checks the array before sorting and removing anything that is not a valid item ie not a number.
+  const sortedList = [...numbers].sort((a, b) => a - b);


Is it necessary to create a copy of numbers first before sorting in this function?

cjyuan · 2026-03-31T17:36:05Z

Sprint-1/implement/dedupe.test.js

 // Given an array with no duplicates
 // When passed to the dedupe function
 // Then it should return a copy of the original array
+test("given an array has no duplicates, it returns a copy of the original array", () => {
+  expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+  expect(dedupe([5, 1, 4])).toEqual([5, 1, 4]);
+});


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 · 2026-03-31T17:38:28Z

Sprint-1/implement/max.test.js

+test("ignores non-number values and returns the max number", () => {
+  expect(findMax(["Not", "A", "Number", 75, 85, 105])).toEqual(105);
+});
+


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 · 2026-03-31T17:41:29Z

Sprint-1/implement/sum.test.js

+test("given an array with decimal float numbers, it should return the total sum", () => {
+  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

AngelaMcLeary added 8 commits March 6, 2026 19:17

Jest test for first case

cb3d8e0

completed dedupe.js and dedupe.test.js formatted with prettier

20843ce

add first 3 Jest tests to max.test.js

4d92ad9

add all Jest tests to max.test.js

0be6961

impemented code for mdeian.js and tested against median.test.js

d95136c

implemented first version of max.js

a0c1ced

fixed max,js implementation, complted sum.js

c938555

formatted code with prettier

5e3891a