Manchester |26-ITP-Sep | Precious Moses | Sprint 1 | Data Groups

Sprint-1/fix/median.js

@@ -6,9 +6,30 @@
 // or contains values that aren't numbers (the function is expected to throw - see the tests).
 
 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");
+  }
+
+  for (const item of list) {
+    if (typeof item !== "number") {
+      throw new Error("calculateMedian requires an array of numbers");
+    }
+  }
+
+  const sortedList = [...list].sort((a, b) => a - b);
   const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (list.length % 2 === 1) {
+    return sortedList[middleIndex];
+  }
+
+  const lowerMiddle = sortedList[middleIndex - 1];
+  const upperMiddle = sortedList[middleIndex];
+  return (lowerMiddle + upperMiddle) / 2;
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,16 @@
-function dedupe() {}
+function dedupe(originalArray) {
+    const uniqueItems = [];
+
+    for (let i = 0; i < originalArray.length; i++) {
+        const currentItem = originalArray[i];
+        const alreadyInArray = uniqueItems.includes(currentItem);
+
+        if (alreadyInArray === false) {
+            uniqueItems.push(currentItem);
+        }
+    }
+
+    return uniqueItems;
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,13 +16,30 @@ 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 of the original array", () => {
+    const input = [1, 2, 3, 4, 5];
+    const result = dedupe(input);
+
+    expect(result).toEqual([1, 2, 3, 4, 5]);
+    expect(result).not.toBe(input);
+});
 
 // 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 with duplicates, it removes them and keeps the first occurrence", () => {
+    expect(dedupe(["a", "a", "b", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+});
+
+test("given an array of numbers with duplicates, it removes them and keeps the first occurrence", () => {
+    expect(dedupe([1, 2, 2, 3, 3, 3, 4, 4, 5, 5])).toEqual([1, 2, 3, 4, 5]);
+    expect(dedupe([5, 5, 2, 1, 1,])).toEqual([5, 2, 1]);
+});

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 +21,20 @@ 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 "Could not calculate a median: calculateMedian requires a non-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('given something that is not an array, returns "Could not calculate a median: calculateMedian requires an array of numbers"', () => {
+    expect(describeMedian("banana")).toBe("Could not calculate a median: calculateMedian requires an array of numbers");
+});

Sprint-1/implement/max.js

@@ -1,4 +1,20 @@
 function findMax(elements) {
+    if(!Array.isArray(elements)) {
+        throw new Error("findMax requires an array of numbers");
+    }
+
+    let max = -Infinity;
+
+    for (const element of elements) {
+        if (typeof element !== "number" || Number.isNaN(element)) {
+            throw new Error("findMax requires an array of numbers");
+        }
+
+        if (element > max) {
+            max = element;
+        }
+    }
+    return max;
 }
 
 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([])).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([7])).toBe(7);
+});
 
 // 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, return the largest overall", () => {
+    expect(findMax([-5, 10, -20, 3])).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 only negative numbers, returns the one closest to zero", () => {
+    expect(findMax([-8, -2, -30])).toBe(-2);
+})
 
 // 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, 2.7, 2.65])).toBe(2.7);
+})
 
 // 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 an array with a non-number, throws an error", () => {
+    expect(() => findMax(["hey", 10, "hi", 60, 10])).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 is not 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 +1,22 @@
-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");
+  }
+
+  let total = 0;
+
+  for (let i = 0; i < list.length; i++) {
+    if (typeof list[i] !== "number") {
+      throw new Error("calculateMean requires an array of numbers");
+    }
+    total += list[i];
+  }
+
+  return total / list.length;
+}
 
 module.exports = calculateMean;

Sprint-1/implement/mean.test.js

@@ -22,29 +22,70 @@ const calculateMean = require("./mean.js");
 // 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");
+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 [7], return 7", () => {
+  expect(calculateMean([7])).toBe(7);
+});
 
 // Given an array containing negative or decimal numbers
 // When passed to calculateMean
 // Then it should return the correct mean
+test("given an array of negative numbers, return the correct mean", () => {
+  expect(calculateMean([-1, -3, -5])).toBe(-3);
+});
+
+test("given an array of decimal numbers, return the correct mean", () => {
+  expect(calculateMean([1.5, 2.5])).toBe(2);
+  expect(calculateMean([0.1, 0.2])).toBeCloseTo(0.15);
+});
 
 // 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 a value that is not 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 at all, 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 with a non-number, throws an error", () => {
+  expect(() => calculateMean([7, "2", 5])).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,18 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("sum requires an array of numbers");
+  }
+
+  let total = 0;
+
+  for (const element of elements) {
+    if (!Number.isFinite(element)) {
+      throw new Error("sum requires an array of numbers");
+    }
+    total += element;
+  }
+
+  return total;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,53 @@ 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 just one number, returns that number", () => {
+  expect(sum([7])).toBe(7);
+});
 
 // 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 total", () => {
+  expect(sum([10, -4, -6])).toBe(0);
+  expect(sum([-1, -2, -3])).toBe(-6);
+});
 
 // 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 total", () => {
+  expect(sum([1.5, 2.5, 3])).toBe(7);
+  expect(sum([0.1, 0.2])).toBeCloseTo(0.3);
+});
 
 // 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 with a non-number, throws an error", () => {
+  expect(() => sum(["hey", 10, "hi", 60, 10])).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 is not 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");
+});
+
+test("given an array containing NaN and Infinity, throws an error", () => {
+  expect(() => sum([1, NaN, 3])).toThrow("sum requires an array of numbers");
+  expect(() => sum([1, Infinity])).toThrow("sum requires an array of number");
+  expect(() => sum([-Infinity, 1])).toThrow("sum requires an array of number");
+});

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 (const element of list) {
     if (element === target) {
       return true;
     }