Complete Sprint-1: Fix median, Implement max/sum/dedupe, and Refactor includes

Author: mahmoudshaabo1984

Sprint-1/fix/median.js

@@ -6,9 +6,35 @@
 // 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;
+  // 1. Guard clause: Check if the input is an array
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  // 2. Filter the array to keep only numbers
+  const numbersOnly = list.filter(
+    (item) => typeof item === "number" && !isNaN(item)
+  );
+
+  // 3. Check for an empty array
+  if (numbersOnly.length === 0) {
+    return null;
+  }
+
+  // 4. Sort the numbers in ascending order
+  numbersOnly.sort((a, b) => a - b);
+
+  // 5. Calculate the middle index
+  const middleIndex = Math.floor(numbersOnly.length / 2);
+
+  // 6. Check if the length is even or odd
+  if (numbersOnly.length % 2 === 0) {
+    // The length is EVEN
+    return (numbersOnly[middleIndex - 1] + numbersOnly[middleIndex]) / 2;
+  } else {
+    // The length is ODD
+    return numbersOnly[middleIndex];
+  }
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,12 @@
-function dedupe() {}
+// dedupe.js
+// Remove duplicate values from an array, preserving the first occurrence of each element
+
+function dedupe(arr) {
+  // Return empty array if input is empty
+
+  // Use Set to automatically remove duplicates, then spread back into an array
+  // Set keeps only unique values in insertion order
+  return [...new Set(arr)];
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -1,27 +1,36 @@
 const dedupe = require("./dedupe.js");
-/*
-Dedupe Array
-
-📖 Dedupe means **deduplicate**
-
-In this kata, you will need to deduplicate the elements of an array
-
-E.g. dedupe(['a','a','a','b','b','c']) target output: ['a','b','c']
-E.g. dedupe([5, 1, 1, 2, 3, 2, 5, 8]) target output: [5, 1, 2, 3, 8]
-E.g. dedupe([1, 2, 1]) target output: [1, 2]
-*/
-
-// Acceptance Criteria:
 
 // 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, returns a copy of the array", () => {
+  expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+});
+
+// Given an array with duplicate strings
+// When passed to the dedupe function
+// Then it should remove duplicates, preserving first occurrence
+test("removes duplicate strings", () => {
+  expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+});
+
+// Given an array with duplicate numbers
+// When passed to the dedupe function
+// Then it should remove duplicates, preserving first occurrence
+test("removes duplicate numbers", () => {
+  expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+});
 
-// Given an array with strings or numbers
+// Given an array with mixed duplicates
 // When passed to the dedupe function
-// Then it should remove the duplicate values, preserving the first occurence of each element
+// Then it should remove duplicates preserving first occurrence
+test("removes duplicates in mixed array", () => {
+  expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,18 @@
+// max.js
+// Find the largest numerical element in an array
+// Non-numeric values are ignored
+
 function findMax(elements) {
+  // Filter to keep only numbers (ignores strings, null, undefined, etc.)
+  const numbersOnly = elements.filter(
+    (item) => typeof item === "number" && !isNaN(item)
+  );
+
+  // If no numbers remain, return -Infinity (consistent with Math.max() behaviour)
+  if (numbersOnly.length === 0) return -Infinity;
+
+  // Math.max with spread returns the largest number
+  return Math.max(...numbersOnly);
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -1,43 +1,50 @@
-/* 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([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("returns the largest number from positive and negative values", () => {
+  expect(findMax([-10, -3, 0, 5, 2])).toBe(5);
+});
 
 // Given an array with just negative numbers
 // When passed to the max function
 // Then it should return the closest one to zero
+test("returns the closest to zero when all numbers are negative", () => {
+  expect(findMax([-5, -1, -3])).toBe(-1);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+test("returns the largest decimal number", () => {
+  expect(findMax([1.1, 2.5, 0.9, 2.4])).toBe(2.5);
+});
 
 // 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-numeric values and returns the max number", () => {
+  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
+// Then it should return -Infinity (same as empty array behaviour)
+test("returns -Infinity when array contains only non-numeric values", () => {
+  expect(findMax(["a", "b", null])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,19 @@
+// sum.js
+// Sum all numerical elements in an array
+// Non-numeric values are ignored
+
 function sum(elements) {
+  // Filter to keep only numbers (ignores strings, null, undefined, etc.)
+  const numbersOnly = elements.filter(
+    (item) => typeof item === "number" && !isNaN(item)
+  );
+
+  // If no numbers found, return 0 (consistent with empty array behaviour)
+  if (numbersOnly.length === 0) return 0;
+
+  // reduce() accumulates all numbers into a single total
+  // 0 is the initial value of the accumulator
+  return numbersOnly.reduce((total, num) => total + num, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -1,36 +1,43 @@
-/* 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([5])).toBe(5);
+});
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+test("correctly sums arrays containing negative numbers", () => {
+  expect(sum([10, -3, 5])).toBe(12);
+});
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+test("correctly sums decimal numbers", () => {
+  expect(sum([1.5, 2.5, 3.0])).toBe(7);
+});
 
 // 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-numeric values 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
+// Then it should return 0 (same as empty array behaviour)
+test("returns 0 when array contains only non-numeric values", () => {
+  expect(sum(["a", null, undefined])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,12 +1,17 @@
-// Refactor the implementation of includes to use a for...of loop
+// includes.js
+// Refactored to use for...of loop instead of a traditional for loop
+// Behaviour is identical — only the loop style changed
 
 function includes(list, target) {
-  for (let index = 0; index < list.length; index++) {
-    const element = list[index];
+  // for...of iterates directly over each element value
+  // No need to manage an index variable manually
+  for (const element of list) {
+    // If the current element matches the target, return true immediately
     if (element === target) {
       return true;
     }
   }
+  // If no element matched after the full loop, return false
   return false;
 }