Sheffield | 26-ITP-jan | Richard Frimpong | Sprint 1 | Data Groups

Sprint-1/fix/median.js

@@ -6,9 +6,30 @@
 // 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;
+  // Return null immediately if the input is not an array
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  // filter() returns a new array, so this does not modify the original input
+  const numbersOnly = list.filter((item) => Number.isFinite(item));
+
+  // Return null if there are no numeric values
+  if (numbersOnly.length === 0) {
+    return null;
+  }
+
+  // Safe to sort directly because numbersOnly is already a new array
+  const sortedNumbers = numbersOnly.sort((a, b) => a - b);
+  const middleIndex = Math.floor(sortedNumbers.length / 2);
+
+  // Even number of values: return the average of the two middle values
+  if (sortedNumbers.length % 2 === 0) {
+    return (sortedNumbers[middleIndex - 1] + sortedNumbers[middleIndex]) / 2;
+  }
+
+  // Odd number of values: return the middle value
+  return sortedNumbers[middleIndex];
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,17 @@
-function dedupe() {}
+// Return a new array with duplicate values removed.
+// Keep the first occurrence of each value.
+
+function dedupe(elements) {
+  const uniqueElements = [];
+
+  for (const element of elements) {
+    // Add the element only if it is not already in the result array
+    if (!uniqueElements.includes(element)) {
+      uniqueElements.push(element);
+    }
+  }
+
+  return uniqueElements;
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -2,7 +2,7 @@ const dedupe = require("./dedupe.js");
 /*
 Dedupe Array
 
-📖 Dedupe means **deduplicate**
+📖 Dedupe means deduplicate
 
 In this kata, you will need to deduplicate the elements of an array
 
@@ -16,12 +16,32 @@ 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", () => {
+  const input = [1, 2, 3];
+  const result = dedupe(input);
+
+  expect(result).toEqual(input);
+  expect(result).not.toBe(input);
+});
 
 // 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 duplicate strings, removes duplicates and preserves first occurrence", () => {
+  expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+});
+
+test("given an array with duplicate numbers, removes duplicates and preserves first occurrence", () => {
+  expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+});
+
+test("given a mixed duplicate order, removes duplicates and preserves first occurrence", () => {
+  expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,16 @@
+// Find the largest numerical value in an array.
+// Non-number values should be ignored.
+
 function findMax(elements) {
+  let maxValue = -Infinity;
+
+  for (const element of elements) {
+    if (Number.isFinite(element) && element > maxValue) {
+      maxValue = element;
+    }
+  }
+
+  return maxValue;
 }
 
-module.exports = findMax;
+module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -15,29 +15,48 @@ 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([42])).toBe(42);
+});
 
 // 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 positive and negative numbers, returns the largest number", () => {
+  expect(findMax([-10, 3, 25, -1])).toBe(25);
+});
 
 // 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 only negative numbers, returns the largest one", () => {
+  expect(findMax([-9, -2, -15, -4])).toBe(-2);
+});
 
 // 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", () => {
+  expect(findMax([1.2, 3.8, 2.4])).toBe(3.8);
+});
 
 // 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, ignores them and returns the max", () => {
+  expect(findMax(["hey", 10, "300", "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 an array with only non-number values, returns -Infinity", () => {
+  expect(findMax(["apple", null, undefined, "banana"])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,16 @@
+// Sum the numerical values in an array.
+// Non-number values should be ignored.
+
 function sum(elements) {
+  let total = 0;
+
+  for (const element of elements) {
+    if (Number.isFinite(element)) {
+      total += element;
+    }
+  }
+
+  return total;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,41 @@ 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 one number, returns that number", () => {
+  expect(sum([7])).toBe(7);
+});
 
 // 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 the correct sum", () => {
+  expect(sum([-5, 10, -2])).toBe(3);
+});
 
 // 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 the correct sum", () => {
+  expect(sum([1.2, 0.6, 0.005])).toBeCloseTo(1.805, 10);
+});
 
 // 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 with non-number values, ignores them and sums only numbers", () => {
+  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 an array with only non-number values, returns 0", () => {
+  expect(sum(["apple", null, undefined, "banana"])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,12 +1,15 @@
 // 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];
+  // Loop through each element in the list using a for...of loop
+  for (const element of list) {
+    // If the current element matches the target, return true
     if (element === target) {
       return true;
     }
   }
+
+  // If the loop finishes without finding the target, return false
   return false;
 }