London|ITP-September-2025|Mariia Serhiienko|Sprint 1|Implement

Sprint-1/fix/median.js

@@ -6,9 +6,26 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (!Array.isArray(list) || list.length === 0) {
+    return null;
+  }
+
+  const filteredNumericArr = list.filter(
+    (el) => typeof el === "number" && Number.isFinite(el)
+  );
+
+  if (filteredNumericArr.length === 0) {
+    return null;
+  }
+
+  const sortedArr = [...filteredNumericArr].sort((a, b) => a - b);
+  const middleIndex = Math.floor(sortedArr.length / 2);
+
+  if (sortedArr.length % 2 !== 0) {
+    return sortedArr[middleIndex];
+  } else {
+    return (sortedArr[middleIndex - 1] + sortedArr[middleIndex]) / 2;
+  }
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,15 @@
-function dedupe() {}
+function dedupe(arr) {
+  if (arr.length === 0) return [];
+
+  const noDupsArr = [];
+  const seenItems = new Set();
+
+  for (const el of arr) {
+    if (!seenItems.has(el)) {
+      noDupsArr.push(el);
+      seenItems.add(el);
+    }
+  }
+  return noDupsArr;
+}
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -12,16 +12,27 @@ E.g. dedupe([1, 2, 1]) target output: [1, 2]
 */
 
 // Acceptance Criteria:
+describe("dedupe", () => {
+  // Given an empty array
+  // When passed to the dedupe function
+  // Then it should return an empty array
+  test("given an empty array, returns an empty array", () => {
+    expect(dedupe([])).toEqual([]);
+  });
 
-// 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");
+  // 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, returns a copy of the original array", () => {
+    const input = [1, 65, 2, 298, 3, 729];
+    expect(dedupe(input)).toEqual([1, 65, 2, 298, 3, 729]);
+  });
 
-// 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 with strings or numbers
-// When passed to the dedupe function
-// Then it should remove the duplicate values, preserving the first occurence of each element
+  // Given an array with strings or numbers
+  // When passed to the dedupe function
+  // Then it should remove the duplicate values, preserving the first occurence of each element
+  test("given an array with duplicates, removes duplicate values preserving the first occurrence", () => {
+    const input = ["a", "b", "a", "c", "b", "d", "e", "d", "c", "a", "b"];
+    expect(dedupe(input)).toEqual(["a", "b", "c", "d", "e"]);
+  });
+});

Sprint-1/implement/max.js

@@ -1,4 +1,16 @@
 function findMax(elements) {
+  if (elements.length === 0) {
+    return -Infinity;
+  } else if (elements.length === 1 && typeof elements[0] === "number") {
+    return elements[0];
+  }
+  const maxEl = Math.max(
+    ...elements.filter((el) => typeof el === "number" && !isNaN(el))
+  );
+
+  if (elements.length > 1) {
+    return maxEl;
+  }
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -12,32 +12,55 @@ We have set things up already so that this file can see your function from the o
 
 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 with non-number values
-// When passed to the max function
-// Then it should return the max and ignore non-numeric values
-
-// Given an array with only non-number values
-// When passed to the max function
-// Then it should return the least surprising value given how it behaves for all other inputs
+describe("findMax", () => {
+  // Given an empty array
+  // When passed to the max function
+  // Then it should return -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([15])).toBe(15);
+  });
+
+  // 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 the largest number", () => {
+    expect(findMax([-112, 7, 3, 20, -2])).toBe(20);
+  });
+
+  // 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 largest number - the closest one to zero", () => {
+    expect(findMax([-653, -80, -7, -4, -12])).toBe(-4);
+  });
+
+  // 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([27.3, 654.1, 45.4, 325.9])).toBe(654.1);
+  });
+
+  // Given an array with non-number values
+  // When passed to the max function
+  // Then it should return the max and ignore non-numeric values
+  test("given an array with non-number values, returns the max and ignores non-numeric values", () => {
+    expect(
+      findMax([7, {}, "Greetings!", 34, null, 15.3, undefined, 30, 3878, NaN])
+    ).toBe(3878);
+  });
+
+  // Given an array with only non-number values
+  // When passed to the max function
+  // Then it should return the least surprising value given how it behaves for all other inputs
+  test("given an array with only non-number values, returns -Infinity", () => {
+    expect(findMax([{}, "Hello!", null, undefined, NaN])).toBe(-Infinity);
+  });
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,19 @@
 function sum(elements) {
+  const numbers = elements.filter(
+    (item) => typeof item === "number" && !isNaN(item)
+  );
+
+  if (numbers.length === 0) return 0;
+
+  const maxDecimalPlaces = numbers.reduce(
+    (currMax, el) => Math.max(currMax, (String(el).split(".") || "").length),
+    0
+  );
+  const decMultiplier = 10 ** maxDecimalPlaces;
+
+  const total = numbers.reduce((acc, el) => acc + el, 0);
+
+  return Math.round((total + Number.EPSILON) * decMultiplier) / decMultiplier;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -9,28 +9,46 @@ E.g. sum(['hey', 10, 'hi', 60, 10]), target output: 80 (ignore any non-numerical
 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 non-number values
-// When passed to the sum function
-// Then it should ignore the non-numerical values and return the sum of the numerical elements
-
-// Given an array with only non-number values
-// When passed to the sum function
-// Then it should return the least surprising value given how it behaves for all other inputs
+describe("sum", () => {
+  // Given an empty array
+  // When passed to the sum function
+  // Then it should return 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([15])).toBe(15);
+  });
+
+  // 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([10, -6, 18, -10])).toBe(12);
+  });
+
+  // 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/float numbers, returns the correct total sum", () => {
+    expect(sum([65.5, 8.45, 32.4, 97.36, 10])).toBe(213.71);
+  });
+
+  // Given an array containing non-number values
+  // When passed to the sum function
+  // Then it should ignore the non-numerical values and return the sum of the numerical elements
+  test("given an array with non-number values, ignores them and returns the sum of numerical elements", () => {
+    expect(sum([10, "hello", 25, null, 5, undefined, {}, 15])).toBe(55);
+  });
+
+  // Given an array with only non-number values
+  // When passed to the sum function
+  // Then it should return the least surprising value given how it behaves for all other inputs
+  test("given an array with only non-number values, returns 0", () => {
+    expect(sum(["Great!", "hi", null, undefined, {}, []])).toBe(0);
+  });
+});

Sprint-1/refactor/includes.js

@@ -1,9 +1,8 @@
 // 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) {
+  for (const el of list) {
+    if (el === target) {
       return true;
     }
   }