Birmingham | 26-ITP-May | Gabriel Pawuoi | Sprint 1 |fix median, implement sum/max/dedupe, refactor includes

Sprint-1/fix/median.js

@@ -5,10 +5,31 @@
 // Hint: Please consider scenarios when 'list' doesn't have numbers (the function is expected to return null)
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
+// WHAT WAS WRONG WITH THE ORIGINAL:
+// 1. It used list.splice() which mutates the original array — the test requires the input not to be modified.
+// 2. It didn't check whether list is actually an array, so it crashed on null/undefined/numbers.
+// 3. It didn't filter out non-numeric values from mixed arrays.
+// 4. It didn't sort the array before finding the middle, so unsorted inputs gave wrong results.
+// 5. It didn't handle even-length arrays (should return the average of the two middle values).
+
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (!Array.isArray(list)) return null;
+
+  // Filter to only numbers (does not modify the original array)
+  const numbers = list.filter((n) => typeof n === "number");
+
+  if (numbers.length === 0) return null;
+
+  // Sort into a new array so the original is never mutated
+  const sorted = [...numbers].sort((a, b) => a - b);
+
+  const mid = Math.floor(sorted.length / 2);
+
+  // Odd length: return the middle element
+  // Even length: return the average of the two middle elements
+  return sorted.length % 2 !== 0
+    ? sorted[mid]
+    : (sorted[mid - 1] + sorted[mid]) / 2;
 }
 
 module.exports = calculateMedian;

Sprint-1/fix/median.test.js

@@ -47,4 +47,4 @@ describe("calculateMedian", () => {
   ].forEach(({ input, expected }) =>
     it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
   );
-});
+});

Sprint-1/implement/dedupe.js

@@ -1 +1,5 @@
-function dedupe() {}
+function dedupe(arr) {
+  return [...new Set(arr)];
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -1,28 +1,21 @@
 const dedupe = require("./dedupe.js");
-/*
-Dedupe Array
 
-📖 Dedupe means **deduplicate**
+test("given an empty array, it returns an empty array", () => {
+  expect(dedupe([])).toEqual([]);
+});
 
-In this kata, you will need to deduplicate the elements of an array
+test("given an array with no duplicates, returns a copy", () => {
+  expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+});
 
-E.g. dedupe(['a','a','a','b','b','c']) returns ['a','b','c']
-E.g. dedupe([5, 1, 1, 2, 3, 2, 5, 8]) returns [5, 1, 2, 3, 8]
-E.g. dedupe([1, 2, 1]) returns [1, 2]
-*/
+test("removes duplicate numbers preserving first occurrence", () => {
+  expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+});
 
-// Acceptance Criteria:
+test("removes duplicate strings preserving first occurrence", () => {
+  expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+});
 
-// Given an empty array
-// When passed to the dedupe function
-// Then it should return an empty array
-test.todo("given an empty array, it returns an empty array");
-
-// Given an array with no duplicates
-// When passed to the dedupe function
-// Then it should return a copy of the original array
-
-// Given an array of strings or numbers
-// When passed to the dedupe function
-// Then it should return a new array with duplicates removed while preserving the 
-// first occurrence of each element from the original array.
+test("given an array with one duplicate, returns array with one element", () => {
+  expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,6 @@
 function findMax(elements) {
+  const numbers = elements.filter(n => typeof n === "number");
+  return numbers.length === 0 ? -Infinity : Math.max(...numbers);
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -1,43 +1,29 @@
-/* Find the maximum element of an array of numbers
-
-In this kata, you will need to implement a function that find the largest numerical element of an array.
-
-E.g. max([30, 50, 10, 40]), target output: 50
-E.g. max(['hey', 10, 'hi', 60, 10]), target output: 60 (sum ignores any non-numerical elements)
-
-You should implement this function in max.js, and add tests for it in this file.
-
-We have set things up already so that this file can see your function from the other file.
-*/
-
 const findMax = require("./max.js");
 
-// Given an empty array
-// When passed to the max function
-// Then it should return -Infinity
-// Delete this test.todo and replace it with a test.
-test.todo("given an empty array, returns -Infinity");
+test("given an empty array, returns -Infinity", () => {
+  expect(findMax([])).toBe(-Infinity);
+});
 
-// Given an array with one number
-// When passed to the max function
-// Then it should return that number
+test("given an array with one number, returns that number", () => {
+  expect(findMax([7])).toBe(7);
+});
 
-// Given an array with both positive and negative numbers
-// When passed to the max function
-// Then it should return the largest number overall
+test("given positive and negative numbers, returns the largest", () => {
+  expect(findMax([-5, 3, -1, 10, 2])).toBe(10);
+});
 
-// Given an array with just negative numbers
-// When passed to the max function
-// Then it should return the closest one to zero
+test("given only negative numbers, returns the closest to zero", () => {
+  expect(findMax([-10, -3, -7])).toBe(-3);
+});
 
-// Given an array with decimal numbers
-// When passed to the max function
-// Then it should return the largest decimal number
+test("given decimal numbers, returns the largest decimal", () => {
+  expect(findMax([1.5, 2.7, 0.3])).toBe(2.7);
+});
 
-// Given an array with non-number values
-// When passed to the max function
-// Then it should return the max and ignore non-numeric values
+test("ignores non-number values", () => {
+  expect(findMax(["hey", 10, "hi", 60, 10])).toBe(60);
+});
 
-// Given an array with only non-number values
-// When passed to the max function
-// Then it should return the least surprising value given how it behaves for all other inputs
+test("given only non-number values, returns -Infinity", () => {
+  expect(findMax(["a", "b"])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,5 @@
 function sum(elements) {
+  return elements.filter(n => typeof n === "number").reduce((acc, n) => acc + n, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -1,36 +1,25 @@
-/* Sum the numbers in an array
-
-In this kata, you will need to implement a function that sums the numerical elements of an array
-
-E.g. sum([10, 20, 30]), target output: 60
-E.g. sum(['hey', 10, 'hi', 60, 10]), target output: 80 (ignore any non-numerical elements)
-*/
-
 const sum = require("./sum.js");
 
-// Acceptance Criteria:
-
-// Given an empty array
-// When passed to the sum function
-// Then it should return 0
-test.todo("given an empty array, returns 0")
+test("given an empty array, returns 0", () => {
+  expect(sum([])).toBe(0);
+});
 
-// Given an array with just one number
-// When passed to the sum function
-// Then it should return that number
+test("given an array with one number, returns that number", () => {
+  expect(sum([42])).toBe(42);
+});
 
-// Given an array containing negative numbers
-// When passed to the sum function
-// Then it should still return the correct total sum
+test("given an array with negative numbers, returns correct sum", () => {
+  expect(sum([-1, -2, -3])).toBe(-6);
+});
 
-// Given an array with decimal/float numbers
-// When passed to the sum function
-// Then it should return the correct total sum
+test("given an array with decimal numbers, returns correct sum", () => {
+  expect(sum([0.1, 0.2])).toBeCloseTo(0.3);
+});
 
-// Given an array containing non-number values
-// When passed to the sum function
-// Then it should ignore the non-numerical values and return the sum of the numerical elements
+test("ignores non-number values", () => {
+  expect(sum(["hey", 10, "hi", 60, 10])).toBe(80);
+});
 
-// Given an array with only non-number values
-// When passed to the sum function
-// Then it should return the least surprising value given how it behaves for all other inputs
+test("given only non-number values, returns 0", () => {
+  expect(sum(["a", "b", null])).toBe(0);
+});