London | 26-ITP-Sep | Alan Mak| Sprint 1 | Data Groups Coursework

Sprint-1/fix/median.js

@@ -6,9 +6,23 @@
 // 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 sortedList = [...list].sort((a, b) => a - b);
+  const middleIndex = Math.floor(sortedList.length / 2);
+
+  if (sortedList.length % 2 === 1) {
+    return sortedList[middleIndex];
+  }
+  return (sortedList[middleIndex - 1] + sortedList[middleIndex]) / 2;
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,12 @@
-function dedupe() {}
+function dedupe(elements) {
+  const dedupedArray = [];
+
+  for (value of elements) {
+    if (!dedupedArray.includes(value)) {
+      dedupedArray.push(value);
+    }
+  }
+  return dedupedArray;
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -13,16 +13,20 @@ E.g. dedupe([1, 2, 1]) returns [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 the copy of same array", () => {
+  expect(dedupe([3, 19, 53, 467])).toEqual([3, 19, 53, 467]);
+});
 
-// 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("given an array of strings or numbers, returns the array with duplicates removed and first occurrence preserved", () => {
+  expect(dedupe([7, "hi", 567, "a", 7, "hi", "b"])).toEqual([
+    7,
+    "hi",
+    567,
+    "a",
+    "b",
+  ]);
+});

Sprint-1/implement/describe-median.js

@@ -1,11 +1,13 @@
 // Don't change this function.
 function calculateMedian(list) {
-  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 (!Array.isArray(list)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
   for (const item of list) {
     if (typeof item !== "number") {
       throw new Error("calculateMedian requires an array of numbers");
@@ -20,6 +22,18 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  try {
+    return "The median is " + calculateMedian(list);
+  } catch {
+    if (list.length === 0) {
+      return "Could not calculate a median: calculateMedian requires a non-empty array";
+    }
+
+    if (!Array.isArray(list)) {
+      return "Could not calculate a median: calculateMedian requires an array of numbers";
+    }
+  }
+}
 
 module.exports = describeMedian;

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

@@ -15,18 +15,17 @@ 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"');
-
-// Given an empty array
-// When passed to describeMedian
-// Then it should return "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('given [1, 2, 3], returns "The median is 2"', () => {
+  expect(describeMedian([1, 2, 3])).toEqual("The median is 2");
+});
+
+test('given empty array, returns "Could not calculate a median: calculateMedian requires a non-empty array"', () => {
+  expect(describeMedian([])).toEqual(
+    "Could not calculate a median: calculateMedian requires a non-empty array"
+  );
+});
+test('given something that isnt an array of numbers, returns "Could not calculate a median: calculateMedian requires an array of numbers"', () => {
+  expect(describeMedian("Non-array")).toEqual(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+});

Sprint-1/implement/max.js

@@ -1,4 +1,24 @@
 function findMax(elements) {
+  if (elements.length === 0) {
+    return -Infinity;
+  }
+
+  if (
+    !elements.every(
+      (currentValue) =>
+        typeof currentValue === "number" && !Number.isNaN(currentValue)
+    )
+  ) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  sortedElements = elements.toSorted((a, b) => a - b);
+
+  return sortedElements[sortedElements.length - 1];
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,50 @@ 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([])).toEqual(-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([100])).toEqual(100);
+});
 
 // 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 largest number overall", () => {
+  expect(findMax([45, -89, 167, -374, 1758, -7432])).toEqual(1758);
+});
 
 // 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([-7, -2, -13, -121, -1345])).toEqual(-2);
+});
 // 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 number", () => {
+  expect(findMax([0.1, 1.2, 23.67, 0.0012, 467.89])).toEqual(467.89);
+});
 // 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")
+test("given an array containing a value that isn't a number, throw Error", () => {
+  expect(findMax([48, 288, "hi", 576])).toThrow(
+    new 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 something that isn't an array, throw Error", () => {
+  expect(findMax("This is a string")).toThrow(
+    new Error("findMax requires an array of numbers")
+  );
+});

Sprint-1/implement/mean.js

@@ -1,3 +1,29 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+
+  if (
+    !list.every(
+      (currentValue) =>
+        typeof currentValue === "number" && !Number.isNaN(currentValue)
+    )
+  ) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+
+  let total = 0;
+
+  for (number of list) {
+    total += number;
+  }
+  const mean = total / list.length;
+
+  return mean;
+}
 
 module.exports = calculateMean;

Sprint-1/implement/mean.test.js

@@ -23,28 +23,47 @@ const calculateMean = require("./mean.js");
 // 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");
+test("given [1, 2, 6], returns 3", () => {
+  expect(calculateMean([1, 2, 6])).toEqual(3);
+});
 
 // Given an array with a single number
 // When passed to calculateMean
 // Then it should return that number
-
+test("given array with single number, return that number", () => {
+  expect(calculateMean([81])).toEqual(81);
+});
 // Given an array containing negative or decimal numbers
 // When passed to calculateMean
 // Then it should return the correct mean
-
+test("given an array with positive and negative numbers, return the correct mean", () => {
+  expect(calculateMean([3, -16, 463, -4563])).toBeCloseTo(-1028.25);
+});
 // Given an empty array
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires a non-empty array")
-
+test("given an empty array, throw an error", () => {
+  expect(calculateMean([])).toThrow("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")
-
+test("given something that isn't an array, throw an error", () => {
+  expect(calculateMean("This is not a string")).toThrow(
+    "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")
-
+test("given no argument, throw an error", () => {
+  expect(calculateMean()).toThrow("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 an array with non-number values, throw an error", () => {
+  expect(calculateMean([3, 5, 9, "greetings", 41])).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,21 @@
 function sum(elements) {
+  if (
+    !elements.every(
+      (currentValue) =>
+        typeof currentValue === "number" && !Number.isNaN(currentValue)
+    )
+  ) {
+    throw new Error("sum requires an array of numbers");
+  }
+  if (!Array.isArray(elements)) {
+    throw new Error("sum requires an array of numbers");
+  }
+
+  let total = 0;
+  for (number of elements) {
+    total += number;
+  }
+  return total;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -8,29 +8,28 @@ E.g. sum(['hey', 10, 'hi', 60, 10]) throws Error("sum requires an array of numbe
 
 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")
-
-// Given an array with just one number
-// When passed to the sum function
-// Then it should return that number
-
-// Given an array containing negative numbers
-// When passed to the sum function
-// Then it should still return the correct total sum
-
-// Given an array with decimal/float numbers
-// When passed to the sum function
-// Then it should return the correct total sum
-
-// Given an array containing a value that isn't a number
-// When passed to the sum function
-// Then it should throw Error("sum 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 sum function
-// Then it should throw Error("sum requires an array of numbers")
+test("given an empty array, returns 0", () => {
+  expect(sum([])).toEqual(0);
+});
+
+test("given an array with one number, returns that number", () => {
+  expect(sum([100])).toEqual(100);
+});
+test("given an array with just negative numbers, returns the correct total sum", () => {
+  expect(sum([-7, -2, -13, -121, -1345])).toEqual(-1488);
+});
+
+test("given an array with decimal numbers, returns the correct total sum", () => {
+  expect(sum([0.1, 1.2, 23.67, 0.0012, 467.89])).toEqual(492.8612);
+});
+
+test("given an array containing a value that isn't a number, throw Error", () => {
+  expect(sum([48, 288, "hi", 576])).toThrow(
+    new Error("sum requires an array of numbers")
+  );
+});
+test("given something that isn't an array, throw Error", () => {
+  expect(sum("This is a string")).toThrow(
+    new Error("sum requires an array of numbers")
+  );
+});

Sprint-1/refactor/includes.js

@@ -1,8 +1,7 @@
 // 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 (element of list) {
     if (element === target) {
       return true;
     }