Manchester | 26-ITP-Sep | Mathew Shaibu | Sprint 1 | Module data groups sprint-1

Sprint-1/fix/median.js

@@ -1,14 +1,20 @@
-// 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
-
-// Hint: Please consider scenarios when 'list' isn't an array, is empty,
-// or contains values that aren't numbers (the function is expected to throw - see the tests).
-
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMedian requires a non-empty array");
+  }
+  if (!list.every((item) => typeof item === "number")) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+  const sorted = [...list].sort((a, b) => a - b);
+  const middleIndex = Math.floor(sorted.length / 2);
+  if (sorted.length % 2 === 0) {
+    return (sorted[middleIndex - 1] + sorted[middleIndex]) / 2;
+  }
+
+  return sorted[middleIndex];
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,11 @@
-function dedupe() {}
+function dedupe(list) {
+  const result = [];
+  for (const item of list) {
+    if (!result.includes(item)) {
+      result.push(item);
+    }
+  }
+  return result;
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -1,28 +1,30 @@
 const dedupe = require("./dedupe.js");
-/*
-Dedupe Array
 
-📖 Dedupe means **deduplicate**
+test("given an empty array, it returns an empty array", () => {
+  expect(dedupe([])).toEqual([]);
+});
 
-In this kata, you will need to deduplicate the elements of an array
+test("returns a a copy with no duplicates", () => {
+  expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+});
 
-E.g. dedupe(['a','a','a','b','b','c']) returns ['a','b','c']
-E.g. dedupe([5, 1, 1, 2, 3, 2, 5, 8]) returns [5, 1, 2, 3, 8]
-E.g. dedupe([1, 2, 1]) returns [1, 2]
-*/
+test("keeps the first occurrence order", () => {
+  expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+});
 
-// Acceptance Criteria:
+test("returns a copy when there are no duplicates", () => {
+  const original = [1, 2, 3, 4];
+  const result = dedupe(original);
+  expect(result).toEqual(original);
+  expect(result).not.toBe(original);
+});
 
-// 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("removes duplicates with mixed types", () => {
+  expect(dedupe([1, "1", 2, "2", 1, "2"])).toEqual([1, "1", 2, "2"]);
+});
 
-// Given an array with no duplicates
-// When passed to the dedupe function
-// Then it should return a copy of the original array
-
-// Given an array of strings or numbers
-// When passed to the dedupe function
-// Then it should return a new array with duplicates removed while preserving the 
-// first occurrence of each element from the original array.
+test("removes duplicates across multiple cases", () => {
+  expect(dedupe([2, 1, 2, 3, 1])).toEqual([2, 1, 3]);
+  expect(dedupe(["a", "b", "a"])).toEqual(["a", "b"]);
+  expect(dedupe([true, true, false])).toEqual([true, false]);
+});

Sprint-1/implement/describe-median.js

@@ -20,6 +20,13 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  try {
+    const median = calculateMedian(list);
+    return "The median is " + median;
+  } catch (error) {
+    return "Could not calculate a median: " + error.message;
+  }
+}
 
 module.exports = describeMedian;

Sprint-1/implement/describe-median.test.js

@@ -1,32 +1,18 @@
-/* Describe the median, or explain why there isn't one
-
-calculateMedian is given to you at the top of describe-median.js. It throws
-when it can't calculate a median. Don't change it.
-
-Implement describeMedian, which calls calculateMedian and returns a sentence
-instead of crashing.
-
-E.g. describeMedian([1, 2, 3]), target output: "The median is 2"
-E.g. describeMedian([]), target output: "Could not calculate a median: calculateMedian requires a non-empty array"
-
-You'll need a try/catch block for this. The catch block must use the error's
-message, so the caller can see what went wrong.
-*/
-
 const describeMedian = require("./describe-median.js");
 
-// Acceptance criteria:
 
-// Given an array of numbers
-// When passed to describeMedian
-// Then it should return "The median is " followed by the median
-// Delete this test.todo and replace it with a test.
-test.todo('given [1, 2, 3], returns "The median is 2"');
+test('given [1, 2, 3], returns "The median is 2"', () => {
+  expect(describeMedian([1, 2, 3])).toBe("The median is 2");
+});
 
-// Given an empty array
-// When passed to describeMedian
-// Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
+test("returns a sentence for an empty array", () => {
+  expect(describeMedian([])).toBe(
+    "Could not calculate a median: calculateMedian requires a non-empty array"
+  );
+});
 
-// Given something that isn't an array of numbers, e.g. "banana"
-// When passed to describeMedian
-// Then it should return "Could not calculate a median: calculateMedian requires an array of numbers"
+test("return a sentence for a non-array", () => {
+  expect(describeMedian("banana")).toBe(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+});

Sprint-1/implement/max.js

@@ -1,4 +1,23 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  if (elements.length === 0) {
+    return -Infinity;
+  }
+
+  if (!elements.every((item) => typeof item === "number")) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  let max = elements[0];
+  for (const item of elements) {
+    if (item > max) {
+      max = item;
+    }
+  }
+  return max;
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -1,43 +1,33 @@
-/* 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]) throws Error("findMax requires an array of numbers") (max can't compare non-numerical elements, so it shouldn't guess)
-
-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");
-
-// Given an array with one number
-// When passed to the max function
-// Then it should return that number
-
-// Given an array with both positive and negative numbers
-// When passed to the max function
-// Then it should return the largest number overall
-
-// Given an array with just negative numbers
-// When passed to the max function
-// Then it should return the closest one to zero
-
-// Given an array with decimal numbers
-// When passed to the max function
-// Then it should return the largest decimal number
-
-// Given an array containing a value that isn't a number
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
-
-// Given something that isn't an array at all, such as "hey", 42 or no argument
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
+test("given an empty array, returns -Infinity", () => {
+  expect(findMax([])).toBe(-Infinity);
+});
+
+test("given an array with one number, returns that number", () => {
+  expect(findMax([7])).toBe(7);
+});
+
+test("returns the largest of positive and negative numbers", () => {
+  expect(findMax([-6, 5, -3, 8])).toBe(8);
+});
+
+test("returns the closest to zero for all negatives", () => {
+  expect(findMax([-9, -2, -6])).toBe(-2);
+});
+
+test("returns the largest decimal number", () => {
+  expect(findMax([1.2, 3.8, 2.6])).toBe(3.8);
+});
+
+test("throws for an array containing a non-number", () => {
+  expect(() => findMax(["hey", 10])).toThrow(
+    new Error("findMax requires an array of numbers")
+  );
+});
+
+test("throws when not given an array", () => {
+  expect(() => findMax("hey")).toThrow(
+    new Error("findMax requires an array of numbers")
+  );
+});

Sprint-1/implement/mean.js

@@ -1,3 +1,18 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+  if (!list.every((item) => typeof item === "number")) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+  let total = 0;
+  for (const item of list) {
+    total += item;
+  }
+  return total / list.length;
+}
 
 module.exports = calculateMean;

Sprint-1/implement/mean.test.js

@@ -1,50 +1,31 @@
-/* Calculate the mean of an array of numbers
-
-In this kata, you will need to implement a function that calculates the mean of an array of numbers.
-
-E.g. calculateMean([1, 2, 6]), target output: 3
-E.g. calculateMean([]) throws Error("calculateMean requires a non-empty array")
-E.g. calculateMean("banana") throws Error("calculateMean requires an array of numbers")
-
-There is no mean of an empty array, and a string isn't an array of numbers, so
-calculateMean should throw rather than return a value. This is the same problem
-calculateMedian solves in the prep and in the fix directory.
-
-You should implement this function in mean.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 calculateMean = require("./mean.js");
 
-// Acceptance criteria:
-
-// Given an array of numbers
-// When passed to calculateMean
-// Then it should return their mean
-// Delete this test.todo and replace it with a test.
-test.todo("given [1, 2, 6], returns 3");
-
-// Given an array with a single number
-// When passed to calculateMean
-// Then it should return that number
-
-// Given an array containing negative or decimal numbers
-// When passed to calculateMean
-// Then it should return the correct mean
-
-// Given an empty array
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires a non-empty array")
-
-// Given a value that isn't an array, e.g. "banana", 42, null or {}
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
-
-// Given no argument at all
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
-
-// Given an array containing a non-number value, e.g. [1, "2", 3]
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
+test("given [1, 2, 6], returns 3", () => {
+  expect(calculateMean([1, 2, 6])).toBe(3);
+});
+
+test("returns the number for a single item array", () => {
+  expect(calculateMean([8])).toBe(8);
+});
+
+test("handles negative and decimal numbers", () => {
+  expect(calculateMean([-2, 4, 3.5])).toBeCloseTo(1.8333);
+});
+
+test("throws for an empty array", () => {
+  expect(() => calculateMean([])).toThrow(
+    new Error("calculateMean requires a non-empty array")
+  );
+});
+
+test("throws when not given an array", () => {
+  expect(() => calculateMean("banana")).toThrow(
+    new Error("calculateMean requires an array of numbers")
+  );
+});
+
+test("throws for an array containing a non-number", () => {
+  expect(() => calculateMean([1, "2", 3])).toThrow(
+    new Error("calculateMean requires an array of numbers")
+  );
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,15 @@
-function sum(elements) {
+function sum(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("sum requires an array of numbers");
+  }
+  if (!list.every(Number.isFinite)) {
+    throw new Error("sum requires an array of numbers");
+  }
+  let total = 0;
+  for (const item of list) {
+    total += item;
+  }
+  return total;
 }
 
 module.exports = sum;