Glasgow | Jan-26-ITP | Alasdair MacDonald | Sprint 1 | Exercises

Sprint-1/fix/median.js

@@ -1,14 +1,31 @@
-// Fix this implementation
-// Start by running the tests for this function
-// If you're in the Sprint-1 directory, you can run `npm test -- fix` to run the tests in the fix directory
+function calculateMedian(list) {
+  // must be an array
+  if (!Array.isArray(list)) {
+    return null;
+  }
 
-// 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).
+  // keep only VALID numeric values (exclude NaN, Infinity)
+  const numbers = list.filter(
+    (value) => typeof value === "number" && Number.isFinite(value)
+  );
 
-function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  // if no numbers exist return null
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // sort numbers without modifying original list
+  const sorted = [...numbers].sort((a, b) => a - b);
+
+  const middle = Math.floor(sorted.length / 2);
+
+  // even length
+  if (sorted.length % 2 === 0) {
+    return (sorted[middle - 1] + sorted[middle]) / 2;
+  }
+
+  // odd length
+  return sorted[middle];
 }
 
-module.exports = calculateMedian;
+module.exports = calculateMedian;

Sprint-1/fix/median.test.js

@@ -1,9 +1,3 @@
-// median.test.js
-
-// Someone has implemented calculateMedian but it isn't
-// passing all the tests...
-// Fix the implementation of calculateMedian so it passes all tests
-
 const calculateMedian = require("./median.js");
 
 describe("calculateMedian", () => {
@@ -13,7 +7,8 @@ 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))
   );
 
   [
@@ -24,7 +19,8 @@ describe("calculateMedian", () => {
     { input: [110, 20, 0], expected: 20 },
     { input: [6, -2, 2, 12, 14], expected: 6 },
   ].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 [3, 1, 2]", () => {
@@ -33,8 +29,9 @@ describe("calculateMedian", () => {
     expect(list).toEqual([3, 1, 2]);
   });
 
-  [ '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))
   );
 
   [
@@ -45,6 +42,12 @@ 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))
   );
-});
+
+  // 🔥 EXTRA test for reviewer feedback
+  it("ignores NaN and Infinity values", () => {
+    expect(calculateMedian([1, 2, NaN, Infinity, 3])).toEqual(2);
+  });
+});

Sprint-1/implement/dedupe.js

@@ -1 +1,13 @@
-function dedupe() {}
+function dedupe(list) {
+  const result = [];
+
+  for (const item of list) {
+    if (!result.includes(item)) {
+      result.push(item);
+    }
+  }
+
+  return result; // ✅ always a NEW array
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -1,27 +1,44 @@
 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, it returns a new array", () => {
+  const input = [1, 2, 3];
+  const result = dedupe(input);
+
+  expect(result).toEqual([1, 2, 3]); // values match
+  expect(result).not.toBe(input);    // 🔥 ensures it's a NEW array
+});
+
+// Given an array with numbers
+// When passed to the dedupe function
+// Then it should remove duplicate values
+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
+// When passed to the dedupe function
+// Then it should remove duplicate values
+test("removes duplicate strings", () => {
+  expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+});
 
-// Given an array with strings or numbers
+// Given an array with duplicates
 // When passed to the dedupe function
-// Then it should remove the duplicate values, preserving the first occurence of each element
+// Then it should preserve the first occurrence order
+test("preserves first occurrence order", () => {
+  expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,13 @@
-function findMax(elements) {
+function findMax(arr) {
+  let max = -Infinity;
+
+  for (let i = 0; i < arr.length; i++) {
+    if (typeof arr[i] === "number" && arr[i] > max) {
+      max = arr[i];
+    }
+  }
+
+  return max;
 }
 
-module.exports = findMax;
+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", () => {
+  expect(findMax([5])).toBe(5);
+});
 
 // 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 positive and negative numbers", () => {
+  expect(findMax([-10, 20, 5, -2])).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 only negative numbers", () => {
+  expect(findMax([-10, -3, -50, -1])).toBe(-1);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+test("given decimal numbers", () => {
+  expect(findMax([1.2, 5.7, 3.3])).toBe(5.7);
+});
 
 // 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", () => {
+  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 the least surprising value
+test("only non-number values returns -Infinity", () => {
+  expect(findMax(["a", "b", "c"])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,13 @@
-function sum(elements) {
+function sum(arr) {
+  let total = 0;
+
+  for (let i = 0; i < arr.length; i++) {
+    if (typeof arr[i] === "number") {
+      total += arr[i];
+    }
+  }
+
+  return total;
 }
 
-module.exports = sum;
+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", () => {
+  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("given negative numbers", () => {
+  expect(sum([10, -5, -5])).toBe(0);
+});
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+test("given decimal numbers", () => {
+  expect(sum([1.5, 2.5, 3])).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
+// Then it should ignore the non-numerical values
+test("ignores non-number values", () => {
+  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 the least surprising value
+test("only non-number values returns 0", () => {
+  expect(sum(["a", "b", "c"])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,13 +1,16 @@
-// 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];
+  // handle non-array safely (optional but solid)
+  if (!Array.isArray(list)) {
+    return false;
+  }
+
+  for (const element of list) {
     if (element === target) {
       return true;
     }
   }
+
   return false;
 }
 
-module.exports = includes;
+module.exports = includes;