Manchester | 26-ITP-Sep | Rahana Suleiman| Sprint 1 | Data Groups Coursework

Sprint-1/fix/median.js

@@ -2,13 +2,39 @@
 // 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;
+  // 1. Check if 'list' is a valid array and not null/undefined
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  // 2. Check if the array is empty
+  if (list.length === 0) {
+    throw new Error("calculateMedian requires a non-empty array");
+  }
+
+  // 3. Check if every item in the array is a valid number (no strings, null, undefined, etc.)
+  for (const item of list) {
+    if (typeof item !== "number" || Number.isNaN(item)) {
+      throw new Error("calculateMedian requires an array of numbers");
+    }
+  }
+
+  // 4. Create a sorted copy of the array so we don't mutate the original input
+  const sorted = [...list].sort((a, b) => a - b);
+  const mid = Math.floor(sorted.length / 2);
+
+  // 5. Calculate median for odd vs even length arrays
+  if (sorted.length % 2 !== 0) {
+    return sorted[mid];
+  } else {
+    return (sorted[mid - 1] + sorted[mid]) / 2;
+  }
 }
 
-module.exports = calculateMedian;
+module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,4 @@
-function dedupe() {}
+function dedupe(arr) {
+  return [... new Set(arr)]
+}
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -18,11 +18,33 @@ E.g. dedupe([1, 2, 1]) returns [1, 2]
 // Then it should return an empty array
 test.todo("given an empty array, it returns an empty array");
 
+it("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.todo("given an array, it returns a copy of the original array");
+
+it("given an array, it returns a copy of the original array", () => {
+const input = [1,2,3];
+const result = dedupe(input)
+
+  expect(result).toEqual([1,2,3]);
+  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.todo("given an array, it returns a duplicate while preserving the first occurrence of each element from the original array");
+
+it("given an array, it removes duplicates while preserving the first occurrence of elements", () => {
+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/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

@@ -23,10 +23,27 @@ const describeMedian = require("./describe-median.js");
 // 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"
+describe("describeMedian", () => {
+  it("given [1, 2, 3], returns {The median is 2}", () => {
+    expect(describeMedian([1, 2, 3])).toEqual("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"
+
+  it("given an empty array, returns the correct error message", () => {
+    expect(describeMedian([])).toEqual(
+      "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"
+  it("given something that isn't an array, returns the correct error message", () => {
+    expect(describeMedian("banana")).toEqual(
+      "Could not calculate a median: calculateMedian requires an array of numbers"
+    );
+  });
+});

Sprint-1/implement/max.js

@@ -1,4 +1,23 @@
 function findMax(elements) {
+  // 1. Check if input is a valid array and not null/undefined
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  // 2. Handle empty array edge case per requirements
+  if (elements.length === 0) {
+    return -Infinity;
+  }
+
+  // 3. Validate that every item in the array is strictly a number (no strings, null, etc.)
+  for (const item of elements) {
+    if (typeof item !== "number" || Number.isNaN(item)) {
+      throw new Error("findMax requires an array of numbers");
+    }
+  }
+
+  // 4. Return the maximum number using Math.max
+  return Math.max(...elements);
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,61 @@ 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");
+describe("findMax", () => {
+  it("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
+  // 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
+  it("given an array with one number, returns that number", () => {
+    expect(findMax([42])).toEqual(42);
+  });
 
-// 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 both positive and negative numbers
+  // When passed to the max function
+  // Then it should return the largest number overall
+  it("given an array with both positive and negative numbers, returns the largest number overall", () => {
+    expect(findMax([30, -50, 10, 40, -5])).toEqual(40);
+  });
 
-// Given an array with decimal numbers
-// When passed to the max function
-// Then it should return the largest decimal number
+  // Given an array with just negative numbers
+  // When passed to the max function
+  // Then it should return the closest one to zero
+  it("given an array with just negative numbers, returns the closest one to zero", () => {
+    expect(findMax([-10, -3, -50, -5])).toEqual(-3);
+  });
 
-// 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 an array with decimal numbers
+  // When passed to the max function
+  // Then it should return the largest decimal number
+  it("given an array with decimal numbers, returns the largest decimal number", () => {
+    expect(findMax([1.5, 2.7, 2.1, 0.4])).toEqual(2.7);
+  });
 
-// 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")
+  // 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")
+  it("given an array containing a value that isn't a number, throws an error", () => {
+    expect(() => findMax(["hey", 10, "hi", 60, 10])).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")
+  it("given something that isn't an array at all, throws an error", () => {
+    expect(() => findMax("hey")).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+    expect(() => findMax(42)).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+    expect(() => findMax()).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+  });
+});

Sprint-1/implement/mean.js

@@ -1,3 +1,25 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  // 1. Check if input is a valid array
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
 
-module.exports = calculateMean;
+  // 2. Check if the array is empty
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+
+  // 3. Validate that every item in the array is strictly a number
+  let sum = 0;
+  for (const item of list) {
+    if (typeof item !== "number" || Number.isNaN(item)) {
+      throw new Error("calculateMean requires an array of numbers");
+    }
+    sum += item;
+  }
+
+  // 4. Return the calculated mean
+  return sum / list.length;
+}
+
+module.exports = calculateMean;

Sprint-1/implement/mean.test.js

@@ -19,32 +19,79 @@ 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");
+describe("calculateMean", () => {
+  // Given an array of numbers
+  // When passed to calculateMean
+  // Then it should return their mean
 
-// Given an array with a single number
-// When passed to calculateMean
-// Then it should return that number
+  it("given [1, 2, 6], returns 3", () => {
+    expect(calculateMean([1, 2, 6])).toEqual(3);
+  });
 
-// Given an array containing negative or decimal numbers
-// When passed to calculateMean
-// Then it should return the correct mean
+  // Given an array with a single number
+  // When passed to calculateMean
+  // Then it should return that number
 
-// Given an empty array
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires a non-empty array")
+  it("given an array with a single number, returns that number", () => {
+    expect(calculateMean([10])).toEqual(10);
+  });
 
-// 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 an array containing negative or decimal numbers
+  // When passed to calculateMean
+  // Then it should return the correct mean
 
-// Given no argument at all
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
+  it("given an array containing negative or decimal numbers, returns the correct mean", () => {
+    expect(calculateMean([6, -2, 8])).toEqual(4); // 6 + (-2) + 8 = 12 / 3 = 4
+    expect(calculateMean([1.5, 2.5])).toEqual(2);
+  });
 
-// 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")
+  // Given an empty array
+  // When passed to calculateMean
+  // Then it should throw Error("calculateMean requires a non-empty array")
+
+  it("given an empty array, throws the correct error", () => {
+    expect(() => calculateMean([])).toThrow(
+      new 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")
+
+  it("given a value that isn't an array (string, number, null, object), throws the correct error", () => {
+    expect(() => calculateMean("banana")).toThrow(
+      new Error("calculateMean requires an array of numbers")
+    );
+    expect(() => calculateMean(42)).toThrow(
+      new Error("calculateMean requires an array of numbers")
+    );
+    expect(() => calculateMean(null)).toThrow(
+      new Error("calculateMean requires an array of numbers")
+    );
+    expect(() => calculateMean({})).toThrow(
+      new 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")
+
+  it("given no argument at all, throws the correct error", () => {
+    expect(() => calculateMean()).toThrow(
+      new 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")
+
+  it("given an array containing a non-number value, throws the correct error", () => {
+    expect(() => calculateMean([1, "2", 3])).toThrow(
+      new Error("calculateMean requires an array of numbers")
+    );
+  });
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,25 @@
 function sum(elements) {
+  // 1. Check if input is a valid array
+  if (!Array.isArray(elements)) {
+    throw new Error("sum requires an array of numbers");
+  }
+
+  // 2. Handle empty array edge case (sum of empty array is 0)
+  if (elements.length === 0) {
+    return 0;
+  }
+
+  // 3. Validate that every item in the array is strictly a number
+  let total = 0;
+  for (const item of elements) {
+    if (typeof item !== "number" || Number.isNaN(item)) {
+      throw new Error("sum requires an array of numbers");
+    }
+    total += item;
+  }
+
+  // 4. Return the calculated sum
+  return total;
 }
 
-module.exports = sum;
+module.exports = sum;