London | 25-ITP-May | Hendrine Zeraua | Sprint 1 | Data Groups

Sprint-1/fix/median.js

@@ -5,10 +5,45 @@
 // 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).
 
-function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
-}
+// function calculateMedian(list) {
+// const middleIndex = Math.floor(list.length / 2);
+// const median = list.splice(middleIndex, 1)[0];
+//  return median;
+// }
 
 module.exports = calculateMedian;
+
+
+// I followed the instructions to fix the calculateMedian function:
+
+// I started by attempting to run the tests in the Sprint-1/fix directory using npm test -- fix.
+// After resolving setup issues and running npx jest, I reviewed the test failures.
+// I then analysed the original code and realised it:
+// - Didn’t sort the array before finding the median
+// - Mutated the original list using .splice()
+// - Didn’t handle non-numeric values or invalid inputs
+// I rewrote the function to:
+// - Filter out all non-numeric values (including NaN)
+// - Handle edge cases like no numbers in the list or invalid input
+// - Sort only the numeric values in ascending order
+// - Correctly calculate the median for both even and odd-length arrays
+// I avoided modifying the original input list by using the spread operator ([...numbers])
+// I used the test results to confirm that the function now works as expected
+
+function calculateMedian(list) {
+
+  if (!Array.isArray(list)) return null;
+
+  const numbers = list.filter(n => typeof n === 'number' && !isNaN(n));
+
+  if (numbers.length === 0) return null;
+
+  const sorted = [...numbers].sort((a, b) => a - b);
+  const mid = Math.floor(sorted.length / 2);
+
+  if (sorted.length % 2 === 0) {
+    return (sorted[mid - 1] + sorted[mid]) / 2;
+  } else {
+    return sorted[mid];
+  }
+}

Sprint-1/fix/median.test.js

@@ -4,6 +4,14 @@
 // passing all the tests...
 // Fix the implementation of calculateMedian so it passes all tests
 
+//   All test cases are passing because:
+//   The calculateMedian function in median.js was updated to:
+//   • Filter out non-numeric values
+//   • Avoid mutating the input array
+//   • Correctly calculate medians for odd and even-length arrays
+//   • Handle unsorted and mixed-type inputs gracefully
+// This confirms the function behaves as expected across a wide range of scenarios.
+
 const calculateMedian = require("./median.js");
 
 describe("calculateMedian", () => {

Sprint-1/implement/dedupe.js

@@ -1 +1,22 @@
-function dedupe() {}
+//I used a Set to track seen values while looping to preserve order. 
+// It passes all test cases including edge cases like empty arrays and type-sensitive inputs.
+
+function dedupe(array) {
+    if (!Array.isArray(array)) return [];
+
+    const seen = new Set();
+    const result = [];
+
+    for (const item of array) {
+      if (!seen.has(item)) {
+        seen.add(item);
+        result.push(item);
+      }
+    }
+
+    return result;
+  }
+
+  module.exports = dedupe;
+
+

Sprint-1/implement/dedupe.test.js

@@ -16,12 +16,27 @@ 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.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 2: No duplicates
+test("given an array with no duplicates, it returns a copy of the original array", () => {
+    expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+  });
 
 // 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("removes duplicates and preserves first occurrence (strings)", () => {
+    expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+  });
+
+  test("removes duplicates and preserves first occurrence (numbers)", () => {
+    expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+  });
+

Sprint-1/implement/max.js

@@ -1,4 +1,30 @@
-function findMax(elements) {
-}
+// function findMax(elements) {
+// }
+
+// module.exports = findMax;
+
 
-module.exports = findMax;
+// In my implementation of findMax:
+//  I first checked if the input is an array. If it isn’t, I return -Infinity as a safe fallback (e.g. for non-array inputs).
+//  Then, I filtered out all non-numeric values using .filter() and typeof el === "number", so that only valid numbers are considered.
+//  If there are no numeric values, I return -Infinity (which is consistent with how Math.max() behaves on an empty array).
+//  Finally, I used Math.max(...numbersOnly) with the spread operator to return the highest value from the filtered list.
+// This approach ensures that the function handles:
+//  Empty arrays
+//  Arrays with all non-numbers
+//  Mixed arrays (e.g., numbers with strings or null)
+//  Positive, negative, and decimal numbers
+//  Without mutating the original array
+// I also confirmed the function passes all tests, including edge cases.
+
+function findMax(elements) {
+    if (!Array.isArray(elements)) return -Infinity;
+
+    const numbersOnly = elements.filter((el) => typeof el === "number");
+
+    if (numbersOnly.length === 0) return -Infinity;
+
+    return Math.max(...numbersOnly);
+  }
+
+  module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,53 @@ 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.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 both positive and negative numbers, returns the largest", () => {
+    expect(findMax([-10, 0, 20, -5, 15])).toBe(20);
+  });
 
 // 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([-100, -1, -50])).toBe(-1);
+  });
 
 // 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([1.1, 2.5, 3.9, 3.8])).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, ignores them and returns max", () => {
+    expect(findMax(["a", 1, "b", 3, null, 2])).toBe(3);
+  });
+
 
 // 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, {}, []])).toBe(-Infinity);
+  });
+

Sprint-1/implement/sum.js

@@ -1,4 +1,27 @@
+// function sum(elements) {
+// }
+
+// module.exports = sum;
+
+/*
+  I implemented a function called sum that takes an array and returns 
+  the total of all numeric values. I made sure to filter out any non-numeric 
+  elements like strings or nulls. 
+
+  I understand that:
+  - If the array is empty or has no numbers, it should return 0.
+  - It needs to handle negative numbers and decimal numbers correctly.
+  - Non-number values should be ignored to prevent errors or incorrect totals.
+*/
+
 function sum(elements) {
-}
+    if (!Array.isArray(elements)) return 0;
+
+    return elements
+      .filter((el) => typeof el === "number")
+      .reduce((total, num) => total + num, 0);
+  }
+
+  module.exports = sum;
+
 
-module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,44 @@ 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.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([-5, -10, -15])).toBe(-30);
+  });
 
 // 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([1.5, 2.5, 3.25])).toBeCloseTo(7.25);
+  });
 
 // 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-numeric values, returns sum of numbers only", () => {
+    expect(sum(["apple", 10, null, 20, "banana", 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
+test("given an array with only non-number values, returns 0", () => {
+    expect(sum(["cat", null, undefined, "dog"])).toBe(0);
+  });
+

Sprint-1/refactor/includes.js

@@ -1,8 +1,32 @@
 // 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];
+//   if (element === target) {
+//   return true;
+//    }
+//  }
+//  return false;
+//  }
+
+// module.exports = includes;
+
+
+/*
+
+I refactored the includes function by changing the for loop to a for...of loop.
+Originally, the function used a standard for loop with an index to go through the array. 
+I replaced that with a for...of loop, which lets me loop directly over each element in the list.
+The logic stayed the same — I checked if the current element matches the target, and returned true if it did. 
+If the loop finishes without finding a match, the function returns false.
+After making this change, I ran all the tests in includes.test.js, and they all passed. 
+This shows the function still works correctly after the refactor.
+
+*/
+
 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;
     }

Sprint-1/refactor/includes.test.js

@@ -1,5 +1,6 @@
 // Refactored version of includes should still pass the tests below:
-
+// All tests passed after refactoring includes.js to use a for...of loop.
+// These tests confirm the function still works correctly.
 const includes = require("./includes.js");
 
 test("returns true when target is in array", () => {