London | 26-ITP-May | Zadri Abdule | Sprint 1 | Data groups

Sprint-1/fix/median.js

@@ -4,10 +4,36 @@
 
 // Hint: Please consider scenarios when 'list' doesn't have numbers (the function is expected to return null)
 // 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 null when input is not an array (tests expect null for invalid input)
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  // Keep only actual numbers. This filters out strings, null, undefined, objects, etc.
+  // We deliberately do not coerce numeric strings (e.g. "3") to numbers — tests expect
+  // non-number values to be ignored rather than parsed.
+  const numericList = list.filter((item) => typeof item === "number" && Number.isFinite(item));
+
+  // If there are no numeric values, return null (the function should not attempt
+  // to compute a median from non-numeric or empty input).
+  if (numericList.length === 0) {
+    return null;
+  }
+
+  // Sort numerically. Using slice() first ensures we don't mutate the filtered
+  // array in case the original caller relies on references; the tests also assert
+  // the original `list` should not be modified.
+  const sorted = numericList.slice().sort((a, b) => a - b);
+
+  // Compute middle index. For odd lengths the middle element is the median.
+  // For even lengths the median is the average of the two middle elements.
+  const middleIndex = Math.floor(sorted.length / 2);
+  const median = sorted.length % 2 === 1
+    ? sorted[middleIndex]
+    : (sorted[middleIndex - 1] + sorted[middleIndex]) / 2;
+
+  // Return the computed median (number).
   return median;
 }
 

Sprint-1/fix/median.test.js

@@ -13,7 +13,8 @@ describe("calculateMedian", () => {
     { input: [1, 2, 3, 4], expected: 2.5 },
     { input: [1, 2, 3, 4, 5, 6], expected: 3.5 },
   ].forEach(({ input, expected }) =>
-    it(`returns the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   [
@@ -24,7 +25,8 @@ describe("calculateMedian", () => {
     { input: [110, 20, 0], expected: 20 },
     { input: [6, -2, 2, 12, 14], expected: 6 },
   ].forEach(({ input, expected }) =>
-    it(`returns the correct median for unsorted array [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the correct median for unsorted array [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   it("doesn't modify the input array [3, 1, 2]", () => {
@@ -33,8 +35,17 @@ describe("calculateMedian", () => {
     expect(list).toEqual([3, 1, 2]);
   });
 
-  [ 'not an array', 123, null, undefined, {}, [], ["apple", null, undefined] ].forEach(val =>
-    it(`returns null for non-numeric array (${val})`, () => expect(calculateMedian(val)).toBe(null))
+  [
+    "not an array",
+    123,
+    null,
+    undefined,
+    {},
+    [],
+    ["apple", null, undefined],
+  ].forEach((val) =>
+    it(`returns null for non-numeric array (${val})`, () =>
+      expect(calculateMedian(val)).toBe(null))
   );
 
   [
@@ -45,6 +56,7 @@ describe("calculateMedian", () => {
     { input: [3, "apple", 1, null, 2, undefined, 4], expected: 2.5 },
     { input: ["banana", 5, 3, "apple", 1, 4, 2], expected: 3 },
   ].forEach(({ input, expected }) =>
-    it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`filters out non-numeric values and calculates the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 });

Sprint-1/implement/dedupe.js

@@ -1 +1,57 @@
-function dedupe() {}
+/*
+ notes:
+
+ - One-line summary: return a new array with duplicates removed, preserving
+   the order of first occurrences.
+ - Input handling: null or undefined -> return [], any other non-array -> throw.
+ - Key idea: use a Set to track values we've seen; push unseen items to result.
+
+ Quick checks:
+ 1) If nothing changes, test with: node -e "console.log(require('./implement/dedupe')([1,1,2]))"
+ 2) If order looks wrong, remember we preserve first occurrences.
+ 3) If unexpected equality (objects), remember objects are compared by reference.
+
+ Tiny TODOs (one small step each):
+ - [ ] Consider accepting array-like objects? (optional)
+ - [ ] Decide whether to treat non-array values consistently (return [] vs throw)
+
+ Short examples:
+ dedupe([1,2,1]) -> [1,2]
+ dedupe(null) -> []
+ dedupe([{a:1},{a:1}]) -> [{a:1},{a:1}]  // different refs stay, not deduped by shape
+
+ Implementation (no behavior changes below):
+*/
+
+function dedupe(arr) {
+    // Quick guard: treat null/undefined as empty lists — doesn't throw, just returns []
+    if (arr === null || arr === undefined) {
+        return [];
+    }
+
+    // If it's not an array, fail fast — makes bugs obvious (helps debugging)
+    if (!Array.isArray(arr)) {
+        throw new TypeError("Input must be an array");
+    }
+
+    // seen: keep track of values we've already added (O(1) lookup)
+    const seen = new Set();
+    // result: build new array, preserve first-seen order
+    const result = [];
+
+    // iterate in order; if unseen -> keep it
+    for (const item of arr) {
+        if (!seen.has(item)) {
+            seen.add(item);
+            result.push(item);
+        }
+    }
+
+    // return the deduped array
+    return result;
+}
+
+module.exports = dedupe;
+
+
+

Sprint-1/implement/dedupe.test.js

@@ -1,4 +1,4 @@
-const dedupe = require("./dedupe.js");
+
 /*
 Dedupe Array
 
@@ -16,13 +16,61 @@ 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");
+
+const dedupe = require("./dedupe.js");
+
+describe("dedupe", () => {
+  test("given an empty array, it returns an empty array", () => {
+    expect(dedupe([])).toEqual([]);
+  });
+});
+
+test("throws for non-array input", () => {
+  expect(() => dedupe(42)).toThrow(TypeError);
+  expect(() => dedupe("string")).toThrow(TypeError);
+  expect(() => dedupe({})).toThrow(TypeError);
+});
+
+test("does not mutate the input array", () => {
+  const input = [1, 2, 3];
+  dedupe(input);
+  expect(input).toEqual([1, 2, 3]);
+});
+
+test("objects are compared by reference", () => {
+    const a = { a: 1 };
+    const b = { a: 1 };
+    expect(dedupe([a, b, a])).toEqual([a, b]);
+});
+
+test('null or undefined returns empty array', () => {
+  expect(dedupe(null)).toEqual([]);
+  expect(dedupe(undefined)).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", () => {
+  expect(dedupe(['a', 'b', 'c'])).toEqual(['a', 'b', 'c']);
+  expect(dedupe([5, 1, 2, 3, 8])).toEqual([5, 1, 2, 3, 8]);
+  expect(dedupe([1, 2])).toEqual([1, 2]);
+  expect(dedupe(['apple', 'banana', 'orange'])).toEqual(['apple', 'banana', 'orange']);
+  expect(dedupe(['Monday', 'Tuesday', 'Wednesday'])).toEqual(['Monday', 'Tuesday', 'Wednesday']);
+});
 // 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 of strings or numbers, it returns a new array with duplicates removed while preserving the first occurrence of each element", () => {
+  expect(dedupe(['a', 'b', 'a', 'c', 'b'])).toEqual(['a', 'b', 'c']);
+  expect(dedupe([1, 2, 1, 3, 2])).toEqual([1, 2, 3]);
+  expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+  expect(dedupe(['apple', 'banana', 'apple', 'orange', 'banana'])).toEqual(['apple', 'banana', 'orange']);
+  expect(dedupe([true, false, true])).toEqual([true, false]);
+});
+
+test("given an array with mixed types, it returns a new array with duplicates removed while preserving the first occurrence", () => {
+  expect(dedupe([1, '1', 2, '2', 1])).toEqual([1, '1', 2, '2']);
+  expect(dedupe(['apple', 1, 'apple', 2])).toEqual(['apple', 1, 2]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,14 @@
 function findMax(elements) {
+    let max = -Infinity;
+    for (const value of elements) {
+        if (typeof value === "number") {
+            max = Math.max(max, value);
+        }
+    }
+    return max;
 }
 
+
+
+
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,54 @@ 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", () => {
+  test("should find the maximum positive number", () => {
+    expect(findMax([1, 2, 3, 4, 5])).toBe(5);
+  });
 
-// Given an array with one number
-// When passed to the max function
-// Then it should return that number
+  test("should return -Infinity if array contains no numbers", () => {
+    expect(findMax(['a', 'b', 'c'])).toBe(-Infinity);
+  });
 
-// 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 one number
+  // When passed to the max function
+  // Then it should return that number
+  test("should handle an array with a single number", () => {
+    expect(findMax([42])).toBe(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
+  test("should find the maximum number in a mixed array", () => {
+    expect(findMax([-10, 0, 10, 20])).toBe(20);
+  });
 
-// 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
+  test("should work correctly with negative numbers", () => {
+    expect(findMax([-10, -20, -30])).toBe(-10);
+  });
 
-// 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 decimal numbers
+  // When passed to the max function
+  // Then it should return the largest decimal number
+  test("should work correctly with decimal numbers", () => {
+    expect(findMax([1.5, 2.5, 3.5])).toBe(3.5);
+  });
 
-// 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
+  // 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("should ignore non-number values" , () => {
+    expect(findMax(["a", "b", "c", 40])).toBe(40);
+  });
+
+  // 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(["a", "b", "c"])).toBe(-Infinity);
+  });
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,11 @@
 function sum(elements) {
+    let total = 0;
+    for (let i = 0; i < elements.length; i++) {
+        if (typeof elements[i] === "number") {
+            total += elements[i];
+        }
+    }
+    return total;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,46 @@ 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")
+describe("sum", () => {
+  test("given an empty array, returns 0", () => {
+    expect(sum([])).toBe(0);
+  });
+
+  test("given an array with just one number, returns that number", () => {
+    expect(sum([42])).toBe(42);
+  });
+});
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
-
+test("should sum an array of positive numbers", () => {
+  expect(sum([1, 2, 3, 4, 5])).toBe(15);
+});
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+test("should sum an array containing negative numbers", () => {
+  expect(sum([-1, -2, -3, -4, -5])).toBe(-15);
+});
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+test("should sum an array of decimal numbers", () => {
+  expect(sum([1.5, 2.5, 3.5])).toBe(7.5);
+});
 
 // 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("should ignore non-number values", () => {
+  expect(sum(["a", "b", "c", 40])).toBe(40);
+});
 
 // 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(["a", "b", "c"])).toBe(0);
+});

Sprint-1/jest.config.js

@@ -0,0 +1,10 @@
+module.exports = {
+  // Treat Sprint-1 as the root for Jest when running from this package
+  rootDir: '.',
+  // Match tests inside the `fix` and `implement` folders
+  // so running `npm test -- fix` will also pick up implement tests like dedupe.test.js
+  testMatch: ['<rootDir>/fix/**/*.test.js', '<rootDir>/implement/**/*.test.js'],
+  // Ignore node_modules inside Sprint-1
+  testPathIgnorePatterns: ['/node_modules/'],
+  modulePathIgnorePatterns: ['/node_modules/'],
+};

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;
     }