West Midlands | 25-ITP-Sept | Georgina Rogers | Sprint 1 | Sprint 1 Coursework

Sprint-1/fix/median.js

@@ -6,9 +6,23 @@
 // 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;
+  if (!Array.isArray(list) || list.length === 0) return null; // Must be an array with atleast one elemnt
+
+  const numbers = list.filter(
+    (x) => typeof x === "number" && Number.isFinite(x)
+  ); // filters out non-numeric values
+
+  if (numbers.length === 0) return null; // Must have at least one number
+
+  const sorted = numbers.slice().sort((a, b) => a - b);
+  // replaced unnecessary array clone 
+
+  const mid = Math.floor(sorted.length / 2); // math.floor gives the correct index
+  if (sorted.length % 2 === 1) {
+    return sorted[mid]; // odd length; median is single centre value
+  } else {
+    return (sorted[mid - 1] + sorted[mid]) / 2; // even length; median is average of two centre values
+  }
 }
 
 module.exports = calculateMedian;

Sprint-1/fix/median.test.js

@@ -1,6 +1,6 @@
 // median.test.js
 
-// Someone has implemented calculateMedian but it isn't
+// Someone has implemented calculateMedian but it isn't 
 // passing all the tests...
 // Fix the implementation of calculateMedian so it passes all tests
 

Sprint-1/implement/dedupe.js

@@ -1 +1,14 @@
-function dedupe() {}
+function dedupe(arr) {
+  if (!Array.isArray(arr) || arr.length === 0) {
+    return [];
+  }
+  const result = []; // array to store unique elements
+  for (let element of arr) {
+    if (!result.includes(element)) {
+      // check if element is not already in result
+      result.push(element); // add unique element to result array
+    }
+  }
+  return result;
+}
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,12 +16,30 @@ 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 the same array", () => {
+    expect(dedupe([1, 2, 3, 4, 5])).toEqual([1, 2, 3, 4, 5]);
+});
+
+// When passed an array
+// It should not return the same array reference
+test("It returns a new array, not the original", () => {
+    const original = [1, 2, 3];
+    const result = dedupe(original);
+    expect(result).not.toBe(original); // Check that the returned array is not the same reference as the original
+});
 
 // 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
+// Then it should remove the duplicate values, preserving the first occurrence of each element
+test("given an array with duplicates, it removes the duplicates", () => {
+    expect(dedupe(['a', 'a', 'b', 'b', 'c'])).toEqual(['a', 'b', 'c']);
+    expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+    expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,18 @@
 function findMax(elements) {
+  if (!Array.isArray(elements) || elements.length === 0) {
+    return -Infinity;
+  }
+    let max = -Infinity;
+
+for (const x of elements) {
+  if (typeof x === "number" && Number.isFinite(x)) {
+    if (x > max) max = x;
+  }
+}
+
+return max;
+// removed .filter as this creates a new array so this avoids unnecessary clones
+
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,48 @@ 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("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("array with positive and negative numbers returns the largest number", () => {
+  expect(findMax([-10, 0, 5, 20, -3])).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("all negative numbers returns the closest to zero", () => {
+  expect(findMax([-50, -20, -3, -40])).toBe(-3);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+test("array with decimal numbers returns the largest decimal", () => {
+  expect(findMax([1.5, 2.7, 0.3, 2.6])).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 and returns the max of numeric values", () => {
+  expect(findMax([10, "hello", 25, null, 15, undefined, 5])).toBe(25);
+});
 
 // 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("array with only non-number values returns -Infinity", () => {
+  expect(findMax(["a", null, undefined, {}, []])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,14 @@
-function sum(elements) {
-}
+function sum(arr) {
+  let total = 0; // variable keeps track of the sum
 
+  for (let element of arr) {
+    // iterate through each element in the array
+    if (Number.isFinite(element)) {
+      // check if the element is a number, without counting NaN or Infinity
+      total += element; // add the number to the total sum
+    }
+  }
+
+  return total; // return the final sum
+}
 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([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 the correct sum", () => {
+  expect(sum([10, -5, 15, -10])).toBe(10);
+});
 
 // 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([1.5, 2.5, 3.0])).toBe(7.0);
+});
 
 // 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 with non-number values, ignores them and returns the sum of numbers", () => {
+  expect(sum([10, "hello", 20, null, 30, undefined, "50"])).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(["hello", null, undefined, "50"])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,13 +1,14 @@
 // 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 (let element of list) {
+    // iterate through each element in the list
     if (element === target) {
-      return true;
+      // check if the current element matches the target
+      return true; // return true if a match is found and exit the function
     }
   }
-  return false;
+  return false; // return false if no match is found after checking all elements
 }
 
 module.exports = includes;