London | 26-ITP-May | Chun Yan Wong | Sprint 1 | Data Groups

Sprint-1/fix/median.js

@@ -6,9 +6,28 @@
 // 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)) return null;
+
+  // Filter out non-numeric values and create a sorted copy
+  const numbers = list
+    .filter((item) => typeof item === "number" && !isNaN(item))
+    .sort((a, b) => a - b);
+
+  // Return null if there are no valid numbers
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  const middleIndex = Math.floor(numbers.length / 2);
+
+  // If even length, take average of the two middle numbers
+  if (numbers.length % 2 === 0) {
+    return (numbers[middleIndex - 1] + numbers[middleIndex]) / 2;
+  }
+
+  // If odd length, return middle number
+  return numbers[middleIndex];
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,5 @@
-function dedupe() {}
+function dedupe(array) {
+  return Array.from(new Set(array));
+}
+
+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];
+    const result = dedupe(input);
+
+    expect(result).toEqual([1, 2, 3]);
+    expect(result).not.toBe(input); // Ensures a new array reference is returned, not the same instance
+  });
 
 // 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 duplicates preserving first occurrence order", () => {
+    expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+  });
+
+  test("given an array of numbers with duplicates, it removes duplicates preserving first occurrence order", () => {
+    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/max.js

@@ -1,4 +1,16 @@
-function findMax(elements) {
+function findMax(list) {
+  if (!Array.isArray(list)) return -Infinity;
+
+  // Filter out any elements that aren't valid numbers
+  const numbers = list.filter(
+    (item) => typeof item === "number" && !isNaN(item)
+  );
+
+  if (numbers.length === 0) {
+    return -Infinity;
+  }
+
+  return Math.max(...numbers);
 }
 
 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([42])).toBe(42);
+  });
 
 // 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 overall", () => {
+    expect(findMax([-10, 20, -5, 50, 0])).toBe(50);
+  });
 
 // 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([-50, -10, -3, -25])).toBe(-3);
+  });
 
 // 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([1.5, 3.14, 2.718, 3.1415])).toBe(3.1415);
+  });
 
 // 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(["hey", 10, "hi", 60, 10])).toBe(60);
+    expect(findMax([null, true, 15, undefined, "20"])).toBe(15);
+  });
 
 // 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", "world", true, null])).toBe(-Infinity);
+  });
+

Sprint-1/implement/sum.js

@@ -1,4 +1,13 @@
 function sum(elements) {
+  if (!Array.isArray(list)) return 0;
+
+  return list.reduce((total, item) => {
+    // Only sum primitive numbers, excluding NaN
+    if (typeof item === "number" && !isNaN(item)) {
+      return total + item;
+    }
+    return total;
+  }, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,42 @@ 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([42])).toBe(42);
+  });
 
 // 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 containing negative numbers, returns the correct total sum", () => {
+    expect(sum([10, -5, 20, -15])).toBe(10);
+  });
 
 // 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([1.5, 2.25, 3.25])).toBe(7);
+  });
 
 // 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 containing non-number values, ignores non-numerical values and returns the sum", () => {
+    expect(sum(["hey", 10, "hi", 60, 10])).toBe(80);
+    expect(sum([null, true, 15, undefined, "20"])).toBe(15);
+  });
 
 // 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(["hello", "world", true, null])).toBe(0);
+  });

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;
     }