London | 26-ITP-Sep | Sakiya Mayow | Sprint 1| coursework/data groups

Sprint-1/fix/median.js

@@ -6,9 +6,27 @@
 // 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((number) => typeof number === "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 !== 0) {
+    return sortedList[middleIndex];
+  }
+
+  return (sortedList[middleIndex - 1] + sortedList[middleIndex]) / 2;
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,7 @@
-function dedupe() {}
+function dedupe(array) {
+  return array.filter((item, index) => {
+    return array.indexOf(item) === index;
+  });
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,13 +16,33 @@ E.g. dedupe([1, 2, 1]) returns [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", () => {
+  const numbers = [1, 2, 3];
+  const result = dedupe(numbers);
+
+  expect(result).toEqual([1, 2, 3]);
+  expect(result).not.toBe(numbers);
+});
+
 // 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 
+// 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 with duplicates, it removes duplicates and preserves the first occurrence", () => {
+  const numbers = [5, 1, 1, 2, 3, 2, 5, 8];
+
+  const result = dedupe(numbers);
+
+  expect(result).toEqual([5, 1, 2, 3, 8]);
+  expect(result).not.toBe(numbers);
+});

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

@@ -21,12 +21,27 @@ const describeMedian = require("./describe-median.js");
 // 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("given an empty array, returns an error message", () => {
+  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("given something that isn't an array of numbers, returns an error message", () => {
+  expect(describeMedian("apple")).toBe(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+});

Sprint-1/implement/max.js

@@ -1,4 +1,14 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+  for (const element of elements) {
+    if (typeof element !== "number") {
+      throw new Error("findMax requires an array of numbers");
+    }
+  }
+
+  return Math.max(...elements);
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,59 @@ 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("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 number", () => {
+  expect(findMax([-5, 10, 3, -2])).toBe(10);
+});
+
 // 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 zero", () => {
+  expect(findMax([-10, -5, -2, -8])).toBe(-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 number", () => {
+  expect(findMax([2.5, 4.7, 1.2, 3.9])).toBe(4.7);
+});
+
 // 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 a non-number array, throws an error", () => {
+  expect(() => findMax(["hello", 10, "apple", 15])).toThrow(
+    "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, throws an error", () => {
+  expect(() => findMax("hey")).toThrow("findMax requires an array of numbers");
+  expect(() => findMax("42")).toThrow("findMax requires an array of numbers");
+  expect(() => findMax()).toThrow("findMax requires an array of numbers");
+});

Sprint-1/implement/mean.js

@@ -1,3 +1,21 @@
-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");
+  }
+  for (const number of list) {
+    if (typeof number !== "number") {
+      throw new Error("calculateMean requires an array of numbers");
+    }
+  }
+  let total = 0;
+  for (const number of list) {
+    total += number;
+  }
+
+  return total / list.length;
+}
 
 module.exports = calculateMean;

Sprint-1/implement/mean.test.js

@@ -23,28 +23,72 @@ 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])).toBe(3);
+});
 
 // Given an array with a single number
 // When passed to calculateMean
 // Then it should return that number
 
+test("given an array with one number, returns that number", () => {
+  expect(calculateMean([6])).toBe(6);
+});
+
 // Given an array containing negative or decimal numbers
 // When passed to calculateMean
 // Then it should return the correct mean
 
+test("given negative and decimal numbers, returns the correct mean", () => {
+  expect(calculateMean([-2, 3.5, 4.5])).toBe(2);
+});
+
 // Given an empty array
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires a non-empty array")
 
+test("given an empty array, throws 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, throws an error", () => {
+  expect(() => calculateMean("banana")).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+  expect(() => calculateMean(42)).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+  expect(() => calculateMean(null)).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+  expect(() => calculateMean({})).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, throws 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 containing a non-number, throws an error", () => {
+  expect(() => calculateMean([1, "2", 3])).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});

Sprint-1/implement/sum.js

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

Sprint-1/implement/sum.test.js

@@ -13,24 +13,49 @@ 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([3])).toBe(3);
+});
+
 // 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([-2, -3, 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 an array with decimal numbers, returns the correct sum", () => {
+  expect(sum([1.5, 2.5, 3])).toBe(7);
+});
+
 // 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")
 
+test("given an array containing a non-number, throws an error", () => {
+  expect(() => sum([1, "2", 3])).toThrow("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 something that isn't an array, throws an error", () => {
+  expect(() => sum("hey")).toThrow("sum requires an array of numbers");
+  expect(() => sum(42)).toThrow("sum requires an array of numbers");
+  expect(() => sum()).toThrow("sum requires an array of numbers");
+});

Sprint-1/refactor/includes.js

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