London | 26-ITP-January | Laura C | Sprint 1 | Data Groups

Sprint-1/fix/median.js

@@ -6,9 +6,27 @@
 // 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;
+  // must be an array
+  if (!Array.isArray(list)) return null;
+
+  // keep only finite numbers (filters out strings, null, undefined, NaN, Infinity)
+  const numbers = list.filter((x) => typeof x === "number" && Number.isFinite(x));
+
+  // if there are no numbers (including empty array), return null
+  if (numbers.length === 0) return null;
+
+  // sort without mutating the original input array
+  const sorted = [...numbers].sort((a, b) => a - b);
+
+  const mid = Math.floor(sorted.length / 2);
+
+  // odd length -> middle element
+  if (sorted.length % 2 === 1) {
+    return sorted[mid];
+  }
+
+  // even length -> average of two middle elements
+  return (sorted[mid - 1] + sorted[mid]) / 2;
 }
 
-module.exports = calculateMedian;
+module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,15 @@
-function dedupe() {}
+function dedupe(input) {
+  if (!Array.isArray(input)) return null;
+
+  const result = [];
+
+  for (const item of input) {
+    if (!result.includes(item)) {
+      result.push(item);
+    }
+  }
+
+  return result;
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,12 +16,33 @@ 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 = ["apple", "banana", 1, 10];
+  const result = dedupe(input);
+
+  expect(result).toEqual(input);
+  expect(result).not.toBe(input); // ensures it's a copy
+});
+
 // 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 duplicate values and preserves first occurrence", () => {
+  expect(dedupe(["a", "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 +1,13 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) return null;
+
+  const numbers = elements.filter(
+    (x) => typeof x === "number" && Number.isFinite(x)
+  );
+
+  if (numbers.length === 0) return -Infinity;
+
+  return Math.max(...numbers);
 }
 
-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([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, returns the largest overall", () => {
+  expect(findMax([1, -10, 50, 3])).toBe(50);
+});
 
 // 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, returns the closest to zero", () => {
+  expect(findMax([-10, -3, -20])).toBe(-3);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+test("given decimal numbers, returns the largest decimal", () => {
+  expect(findMax([1.5, 10.5, 0.5])).toBe(10.5);
+});
 
 // 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-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
+test("given only non-number values, returns -Infinity", () => {
+  expect(findMax(["apple", "banana"])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,19 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) return null;
+
+  const numbers = elements.filter(
+    (x) => typeof x === "number" && Number.isFinite(x)
+  );
+
+  if (numbers.length === 0) return 0;
+
+  let total = 0;
+
+  for (const number of numbers) {
+    total += number;
+  }
+
+  return total;
 }
 
-module.exports = sum;
+module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -10,27 +10,45 @@ 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("given negative numbers, returns correct sum", () => {
+  expect(sum([1, -1, -100])).toBe(-100);
+});
 
 // 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, returns correct sum", () => {
+  expect(sum([1.5, 10.5, 0.5])).toBeCloseTo(12.5);
+});
 
 // 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-number values", () => {
+  expect(sum(["apple", 10, "banana", 5])).toBe(15);
+});
 
 // 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
+test("given only non-number values, returns 0", () => {
+  expect(sum(["apple", "banana"])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,13 +1,10 @@
-// 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 (const element of list) {
     if (element === target) {
       return true;
     }
   }
   return false;
 }
 
-module.exports = includes;
+module.exports = includes;