London | May-2025 | Halimatou Saddiyaa | Module-Data-Groups | Sprint 1

Sprint-1/fix/median.js

@@ -6,9 +6,33 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  // To correct the implementation with the test feedback, we need first to ensure that the function detects that list is an array of numbers and returns null if it is not.
+  if (!Array.isArray(list)) return null;
+
+  // Secondly, we need to implement a function that filter out non numeric values and NAN.
+  const numbers = list.filter(
+    (item) => typeof item === "number" && !Number.isNaN(item)
+  );
+
+  // Thirdly, we need  to make sure that the function returns null if the list is empty or has no numeric values.
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // Then, we need to make sure that the function sorts the numbers in ascending order before calculating the median.
+  const sorted = [...numbers].sort((a, b) => a - b);
+  const middleIndex = Math.floor(sorted.length / 2);
+
+  // Finally, we need to make sure that the function returns the average of the two middle numbers if the list has an even number of elements.
+  if (sorted.length % 2 === 0) {
+    return (sorted[middleIndex - 1] + sorted[middleIndex]) / 2;
+  } else {
+    return sorted[middleIndex];
+  }
 }
 
+//const middleIndex = Math.floor(list.length / 2);
+//const median = list.splice(middleIndex, 1)[0];
+//return median;}
+
 module.exports = calculateMedian;

Sprint-1/fix/median.test.js

@@ -13,7 +13,8 @@ describe("calculateMedian", () => {
     { input: [1, 2, 3, 4], expected: 2.5 },
     { input: [1, 2, 3, 4, 5, 6], expected: 3.5 },
   ].forEach(({ input, expected }) =>
-    it(`returns the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   [
@@ -22,7 +23,8 @@ describe("calculateMedian", () => {
     { input: [4, 2, 1, 3], expected: 2.5 },
     { input: [6, 1, 5, 3, 2, 4], expected: 3.5 },
   ].forEach(({ input, expected }) =>
-    it(`returns the correct median for unsorted array [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the correct median for unsorted array [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   it("doesn't modify the input array [1, 2, 3]", () => {
@@ -31,8 +33,17 @@ describe("calculateMedian", () => {
     expect(list).toEqual([1, 2, 3]);
   });
 
-  [ 'not an array', 123, null, undefined, {}, [], ["apple", null, undefined] ].forEach(val =>
-    it(`returns null for non-numeric array (${val})`, () => expect(calculateMedian(val)).toBe(null))
+  [
+    "not an array",
+    123,
+    null,
+    undefined,
+    {},
+    [],
+    ["apple", null, undefined],
+  ].forEach((val) =>
+    it(`returns null for non-numeric array (${val})`, () =>
+      expect(calculateMedian(val)).toBe(null))
   );
 
   [
@@ -43,6 +54,13 @@ describe("calculateMedian", () => {
     { input: [3, "apple", 1, null, 2, undefined, 4], expected: 2.5 },
     { input: ["banana", 5, 3, "apple", 1, 4, 2], expected: 3 },
   ].forEach(({ input, expected }) =>
-    it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`filters out non-numeric values and calculates the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
-});
+
+  it("ignores NaN and calculates correct median", () => {
+    expect(calculateMedian([1, 2, NaN, 3, 4])).toBe(2.5);
+    expect(calculateMedian([NaN, NaN, 3])).toBe(3);
+    expect(calculateMedian([NaN, NaN])).toBe(null);
+  });
+});

Sprint-1/implement/dedupe.js

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

Sprint-1/implement/dedupe.test.js

@@ -16,12 +16,25 @@ E.g. dedupe([1, 2, 1]) target output: [1, 2]
 // 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");
+
+test("given an empty array, it returns an empty array", () => {
+  expect(dedupe([])).toEqual([]);
+});
 
 // 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 with no duplicates, it returns a copy of the original array", () => {
+  expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+  expect(dedupe(["a", "b", "c"])).toEqual(["a", "b", "c"]);
+});
+
 // Given an array with strings or numbers
 // When passed to the dedupe function
 // Then it should remove the duplicate values, preserving the first occurence of each element
+
+test("given an array with strings or numbers, it removes duplicates preserving the first occurrence", () => {
+  expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+  expect(dedupe(["a", "b", "a", "c"])).toEqual(["a", "b", "c"]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,9 @@
-function findMax(elements) {
+function findMax(arr) {
+  const numbers = arr.filter((item) => typeof item === "number");
+  if (numbers.length === 0) {
+    return -Infinity;
+  }
+  return Math.max(...numbers);
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,57 @@ const findMax = require("./max.js");
 // 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([12])).toBe(12);
+});
+
 // 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 an array with both positive and negative numbers, returns the largest number overall", () => {
+  expect(findMax([-15, 30, 0, 10, -5])).toBe(30);
+});
+
 // Given an array with just negative numbers
 // When passed to the max function
 // Then it should return the closest one to zero
 
+test("given an array with just negative numbers, returns the closest one to zero", () => {
+  expect(findMax([-50, -30, -5, -20])).toBe(-5);
+});
+
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
 
+test("given an array with decimal numbers, returns the largest decimal number", () => {
+  expect(findMax([1.8, 2.7, 0.3, 3.9])).toBe(3.9);
+});
+
 // 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("given an array with non-number values, returns the max and ignores non-numeric values", () => {
+  expect(findMax(["hello", 10, "world", 50, 20])).toBe(50);
+});
+
 // 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
+
+// As this is a max function, it should return -Infinity as the least surprising value.
+
+test("given an array with only non-number values, returns -Infinity", () => {
+  expect(findMax(["hello", "world", "hi", "there"])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,7 @@
-function sum(elements) {
+function sum(arr) {
+  return arr
+    .filter((item) => typeof item === "number")
+    .reduce((total, num) => total + num, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,49 @@ const sum = require("./sum.js");
 // 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 just one number, returns that number", () => {
+  expect(sum([11])).toBe(11);
+});
+
 // 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 containing negative numbers, returns the correct total sum", () => {
+  expect(sum([-10, -20, -30])).toBe(-60);
+});
+
 // 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/float numbers, returns the correct total sum", () => {
+  expect(sum([5.4, 2.3, 4.3])).toBe(12.0);
+});
+
 // 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("given an array containing non-number values, ignores non-numerical values and returns the sum of numerical elements", () => {
+  expect(sum(["hello", 10, "world", 20, 30])).toBe(60);
+});
+
 // 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
+
+//The least surprising value should be 0, as there are no numeric values to sum.
+
+test("given an array with only non-number values, returns 0", () => {
+  expect(sum(["hello", "world", "hi", "there"])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,8 +1,7 @@
 // Refactor the implementation of includes to use a for...of loop
 
 function includes(list, target) {
-  for (let index = 0; index < list.length; index++) {
-    const element = list[index];
+  for (const element of list) {
     if (element === target) {
       return true;
     }