Glasgow | 26-ITP-May | Niangh Ciang | Sprint 1 | Exercises

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)) {
+    return null;
+  }
+  const numbersOnly = list.filter(Number.isFinite);
+
+  if (numbersOnly.length === 0) {
+    return null;
+  }
+
+  const sortedList = [...numbersOnly].sort((a, b) => a - b);
+
+  const middleIndex = Math.floor(sortedList.length / 2);
+
+  if (sortedList.length % 2 !== 0) {
+    return sortedList[middleIndex];
+  } else {
+    const firstMiddle = sortedList[middleIndex - 1];
+    const secondMiddle = sortedList[middleIndex];
+    return (firstMiddle + secondMiddle) / 2;
+  }
 }
 
 module.exports = calculateMedian;

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 +35,21 @@ 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 (${val})`, () => expect(calculateMedian(val)).toBe(null))
+  it("filters out NaN, Infinity, and -Infinity", () => {
+    expect(calculateMedian([NaN, Infinity, -Infinity, 1, 2, 3])).toEqual(2);
+  });
+
+  [
+    "not an array",
+    123,
+    null,
+    undefined,
+    {},
+    [],
+    ["apple", null, undefined],
+  ].forEach((val) =>
+    it(`returns null for non-numeric array (${val})`, () =>
+      expect(calculateMedian(val)).toBe(null))
   );
 
   [
@@ -45,6 +60,7 @@ 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 +1,5 @@
-function dedupe() {}
+function dedupe(array) {
+  if (!Array.isArray(array)) return [];
+  return [...new Set(array)];
+}
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -14,15 +14,48 @@ E.g. dedupe([1, 2, 1]) returns [1, 2]
 // Acceptance Criteria:
 
 // 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");
+describe("dedupe", () => {
+  test("returns an empty array when passed 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
+  // Given an array with no duplicates
+  test("returns a copy of the original array when there are no duplicates", () => {
+    expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+    expect(dedupe(["a", "b", "c"])).toEqual(["a", "b", "c"]);
+    expect(dedupe(["apple", "banana", "cherry"])).toEqual([
+      "apple",
+      "banana",
+      "cherry",
+    ]);
+  });
 
-// 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.
+  // Given an array of strings or numbers
+  test("removes duplicates from an array of numbers", () => {
+    expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+    expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+    expect(dedupe([1, 1, 2, 2, 3, 3, 4, 4])).toEqual([1, 2, 3, 4]);
+  });
+  test("removes duplicates from an array of strings", () => {
+    expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+    expect(
+      dedupe(["apple", "banana", "apple", "banana", "cherry", "cherry"])
+    ).toEqual(["apple", "banana", "cherry"]);
+    expect(dedupe(["cat", "dog", "cat", "bird"])).toEqual([
+      "cat",
+      "dog",
+      "bird",
+    ]);
+  });
+  // Given an array with mixed types
+  test("removes duplicates from an array with mixed types", () => {
+    expect(dedupe([1, "1", 2, "2", 1, "1"])).toEqual([1, "1", 2, "2"]);
+    expect(dedupe(["apple", 1, "banana", 2, "apple", 1])).toEqual([
+      "apple",
+      1,
+      "banana",
+      2,
+    ]);
+    expect(dedupe([true, false, true, false])).toEqual([true, false]);
+  });
+});

Sprint-1/implement/max.js

@@ -1,4 +1,16 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) return -Infinity;
+  let max = -Infinity;
+
+  for (const element of elements) {
+    if (typeof element === "number") {
+      if (element > max) {
+        max = element;
+      }
+    }
+  }
+
+  return max;
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -12,32 +12,38 @@ 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", () => {
+  test("returns -Infinity when passed an empty array", () => {
+    expect(findMax([])).toEqual(-Infinity);
+  });
+
+  // Given an array with one number
+  test("returns the number itself when passed an array with one number", () => {
+    expect(findMax([42])).toEqual(42);
+  });
+
+  // Given an array with both positive and negative numbers
+  test("returns the largest number with both positive and negative numbers", () => {
+    expect(findMax([-10, 0, 10, 20, -20])).toEqual(20);
+  });
+
+  // Given an array with just negative numbers
+  test("returns the largest number with negative numbers", () => {
+    expect(findMax([-10, -20, -30, -4, -8, -1])).toEqual(-1);
+  });
+
+  // Given an array with decimal numbers
+  test("returns the largest number with decimal numbers", () => {
+    expect(findMax([-5, 2.3, 7.5, 3.9, 2.1])).toEqual(7.5);
+  });
+
+  // Given an array with non-number values
+  test("returns the largest number when the array contains non-numeric values", () => {
+    expect(findMax(["hey", 10, "hi", 60, 10])).toEqual(60);
+  });
+
+  // Given an array with only non-number values
+  test("returns -Infinity when the array contains only non-numeric values", () => {
+    expect(findMax(["hey", "hi", "hello"])).toEqual(-Infinity);
+  });
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,15 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) return 0;
+
+  let total = 0;
+
+  for (const element of elements) {
+    if (typeof element === "number") {
+      total += element;
+    }
+  }
+  total = Number(total.toFixed(2));
+  return total;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,43 @@ 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")
-
-// 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", () => {
+  test("returns 0 when passed an empty array", () => {
+    expect(sum([])).toEqual(0);
+  });
+
+  // Given an array with just one number
+  // When passed to the sum function
+  // Then it should return that number
+  test("returns the number itself when passed an array with one number", () => {
+    expect(sum([4])).toEqual(4);
+  });
+
+  // Given an array containing negative numbers
+  // When passed to the sum function
+  // Then it should still return the correct total sum
+  test("returns the correct total sum when passed an array with negative numbers", () => {
+    expect(sum([-10, 20, -30, 40])).toEqual(20);
+  });
+
+  // Given an array with decimal/float numbers
+  // When passed to the sum function
+  // Then it should return the correct total sum
+  test("returns the correct total sum when passed an array with decimal numbers", () => {
+    expect(sum([-5, 2.3, 7.5, 3.9, 2.1])).toEqual(10.8);
+  });
+
+  // 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("returns the correct total sum when passed an array with non-numeric values", () => {
+    expect(sum(["hey", 10, "hi", 60, 10])).toEqual(80);
+  });
+
+  // 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("returns 0 when passed an array with only non-numeric values", () => {
+    expect(sum(["hello", "kitty", "cc"])).toEqual(0);
+  });
+});

Sprint-1/refactor/includes.js

@@ -1,6 +1,6 @@
 // Refactor the implementation of includes to use a for...of loop
 
-function includes(list, target) {
+/*function includes(list, target) {
   for (let index = 0; index < list.length; index++) {
     const element = list[index];
     if (element === target) {
@@ -9,5 +9,15 @@ function includes(list, target) {
   }
   return false;
 }
+*/
+
+function includes(list, target) {
+  for (const element of list) {
+    if (element === target) {
+      return true;
+    }
+  }
+  return false;
+}
 
 module.exports = includes;

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

@@ -0,0 +1,16 @@
+const fs = require("fs");
+
+const raw = fs.readFileSync("input.txt", "utf8");
+
+const lines = raw.split("\n");
+const numbers = lines.map(Number);
+function findFinalFrequency(nums) {
+  let total = 0;
+
+  for (const n of nums) {
+    total += n;
+  }
+
+  return total;
+}
+console.log(findFinalFrequency(numbers));