London | 26-ITP-May | Vitalii Kmit | Sprint 1 | Exercises

Sprint-1/fix/median.js

@@ -6,9 +6,22 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
+  if (!Array.isArray(list)) return null;
+
+  list = list.filter((item) => typeof item === "number");
+  list.sort((a, b) => a - b);
+
+  if (list.length <= 1) {
+    return null;
+  }
+
   const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+
+  if (list.length % 2 === 0) {
+    return (list[middleIndex] + list[middleIndex - 1]) / 2;
+  } else {
+    return list[middleIndex];
+  }
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,15 @@
-function dedupe() {}
+function dedupe(list) {
+  const seen = {};
+  const result = [];
+
+  for (const item of list) {
+    if (seen[item] === undefined) {
+      seen[item] = true;
+      result.push(item);
+    }
+  }
+
+  return result;
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,13 +16,52 @@ 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 the original array", () => {
+  expect(dedupe([5, 2, 1])).toEqual([5, 2, 1]);
+});
 
 // 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 and numbers, it returns a new array with duplicates removed while preserving the first occurance of each element from the original array", () => {
+  expect(dedupe(["hi", "hi", 4, 5, 6, 6])).toEqual(["hi", 4, 5, 6]);
+});
+
+test("given an array of strings with duplicates, it removes duplicates while preserving first occurrence", () => {
+  expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+});
+
+test("given an array of numbers with duplicates, it preserves the order of first occurrences", () => {
+  expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+});
+
+test("given an array with a single element, it returns that element", () => {
+  expect(dedupe([42])).toEqual([42]);
+  expect(dedupe(["hello"])).toEqual(["hello"]);
+});
+
+test("given an array where every element is the same, it returns a single-element array", () => {
+  expect(dedupe([7, 7, 7, 7])).toEqual([7]);
+  expect(dedupe(["x", "x", "x"])).toEqual(["x"]);
+});
+
+test("preserves the order of first occurrences with mixed types", () => {
+  expect(dedupe([1, "a", 1, "b", "a", 2])).toEqual([1, "a", "b", 2]);
+});
+
+test("returns a new array, not the original", () => {
+  const input = [1, 2, 2, 3];
+  const result = dedupe(input);
+  expect(result).toEqual([1, 2, 3]);
+  expect(result).not.toBe(input);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,13 @@
 function findMax(elements) {
+  let max = -Infinity;
+
+  for (i of elements) {
+    if (typeof i === "number" && !isNaN(i) && i > max) {
+      max = i;
+    }
+  }
+
+  return max;
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -15,29 +15,54 @@ 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");
+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);
+  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, returns the largest overall", () => {
+  expect(findMax([30, 50, 10, 40])).toBe(50);
+  expect(findMax([-10, 5, -3, 20, -1])).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 only negative numbers, returns the closest to zero", () => {
+  expect(findMax([-10, -3, -7, -1])).toBe(-1);
+  expect(findMax([-50, -20, -100])).toBe(-20);
+});
 
 // 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, 3.2, 0.9, 2.8])).toBe(3.2);
+  expect(findMax([-1.1, -0.5, -2.3])).toBe(-0.5);
+});
 
 // 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 mixed values, ignores non-numeric values and returns the max number", () => {
+  expect(findMax(["hey", 10, "hi", 60, 10])).toBe(60);
+  expect(findMax([true, 5, null, 12, "hello", 8])).toBe(12);
+});
 
 // 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 only non-number values, returns -Infinity", () => {
+  expect(findMax(["hey", "hi", true, null])).toBe(-Infinity);
+  expect(findMax([{}, [], undefined])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,13 @@
 function sum(elements) {
+  let sum = 0;
+
+  for (i of elements) {
+    if (typeof i === "number" && !isNaN(i)) {
+      sum += i;
+    }
+  }
+
+  return sum;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -8,29 +8,49 @@ 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")
+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([42])).toBe(42);
+  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 sum", () => {
+  expect(sum([10, -3, 5, -2])).toBe(10);
+  expect(sum([-10, -20, -30])).toBe(-60);
+});
 
 // 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 sum", () => {
+  expect(sum([1.5, 2.5, 3])).toBe(7);
+  expect(sum([0.1, 0.2, 0.3])).toBeCloseTo(0.6); // safer for floating point
+});
 
 // 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 mixed values, ignores non-numbers and sums the numbers", () => {
+  expect(sum(["hey", 10, "hi", 60, 10])).toBe(80);
+  expect(sum([true, 5, null, 12, "hello", 8])).toBe(25);
+});
 
 // 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 only non-number values, returns 0", () => {
+  expect(sum(["hey", "hi", true, null])).toBe(0);
+  expect(sum([{}, [], undefined])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,8 +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];
+  // for (let index = 0; index < list.length; index++) {
+  for (const element of list) {
     if (element === target) {
       return true;
     }