London | 26-ITP-May | Martin Mwaka | Sprint 1 | Exercises

Sprint-1/fix/median.js

@@ -6,9 +6,23 @@
 // 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;
+  // return null if it is not an array
+  if (!Array.isArray(list)) return null;
+
+  // filter only numbers from array and sort the filtered array.  If no numbers return null
+  const numbers = list
+    .filter((item) => typeof item === "number")
+    .sort((a, b) => a - b);
+  if (numbers.length === 0) return null;
+
+  // get numbers array mid point
+  const middleIndex = Math.floor(numbers.length / 2);
+  // check if numbers array length is even
+  const isEven = numbers.length % 2 === 0;
+  // calculate median based on whether the numbers array length is even or odd
+  return isEven
+    ? (median = (numbers[middleIndex - 1] + numbers[middleIndex]) / 2)
+    : numbers[middleIndex];
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,7 @@
-function dedupe() {}
+function dedupe(array) {
+  // return empty array if empty input
+  if (array.length === 0) return [];
+  return Array.from(new Set(array));
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,13 +16,29 @@ 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([4, 5, 6])).toEqual([4, 5, 6]);
+});
 
 // 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 a number array with duplicates, it returns a new array without duplicates", () => {
+  expect(dedupe([1, 2, 3, 2, 3])).toEqual([1, 2, 3]);
+});
+
+test("given a string array with duplicates, it returns a new array without duplicates", () => {
+  expect(dedupe(["a", "a", "b", "c"])).toEqual(["a", "b", "c"]);
+});
+
+test("given a mixed array with duplicates, it returns a new array without duplicates", () => {
+  expect(dedupe([1, "a", "a", "b", "c"])).toEqual([1, "a", "b", "c"]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,8 @@
 function findMax(elements) {
+  // filter to return only numbers or an empty array
+  const numbers = elements.filter((item) => Number.isFinite(item));
+  // if numbers present in array return largest number or return -Infinity for empty array
+  return numbers.length ? Math.max(...numbers) : -Infinity;
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,45 @@ 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([2])).toBe(2);
+});
 // 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 positive and negative numbers, returns largest overall number", () => {
+  expect(findMax([5, -3, 15])).toBe(15);
+});
 // 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 negative numbers, returns number closest to zero", () => {
+  expect(findMax([-5, -3, -15])).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 largest decimal number", () => {
+  expect(findMax([10.5, 2.6, 8.1])).toBe(10.5);
+});
 
 // 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 a mixed array with non-number values, returns largest number and ignore non-numbers", () => {
+  expect(findMax([7, 3, "hello", "#"])).toBe(7);
+});
 // 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 of non-number values, returns -Infinity", () => {
+  expect(findMax(["#", "hello", "?"])).toBe(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,8 @@
 function sum(elements) {
+  // filter out the numbers and sum them up
+  return elements
+    .filter((item) => Number.isFinite(item))
+    .reduce((acc, num) => acc + num, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,39 @@ 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 one number, returns the number", () => {
+  expect(sum([1])).toBe(1);
+});
 
 // 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 of only negative numbers, returns the sum", () => {
+  expect(sum([-1, -2])).toBe(-3);
+});
 // 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 sum", () => {
+  expect(sum([2, 3.5, 4])).toBe(9.5);
+});
 // 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
+// Then it should ignore the non-numerical values and return the sum of the numerical
+test("given an array containing non-number values, returns sum of number values", () => {
+  expect(sum([5, "#", "hello", 2])).toBe(7);
+});
 
 // 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 of non-number values, returns 0", () => {
+  expect(sum(["#", "hello"])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,11 +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) {
-      return true;
-    }
+  for (const number of list) {
+    if (number === target) return true;
   }
   return false;
 }

Sprint-1/stretch/aoc-2018-day1/solution.js

@@ -0,0 +1,14 @@
+const fs = require("fs");
+const path = require("path");
+const data = fs.readFileSync(path.join(__dirname, "input.txt"), "utf-8");
+const total = data
+  .split("\n")
+  .map((line) => line.trim())
+  .filter((line) => line !== "")
+  .map(Number);
+
+const mapFrequency = (changes) => changes.reduce((acc, num) => acc + num, 0);
+console.log(mapFrequency([+1, +1, +1])); // 3
+console.log(mapFrequency([+1, +1, -2])); // 0
+console.log(mapFrequency([-1, -2, -3])); // -6
+console.log(mapFrequency(total)); // 529;