London | 26-ITP-May | Raihan Sharif | Sprint 1 | Exercises

Sprint-1/fix/median.js

@@ -6,9 +6,31 @@
 // 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-numbers and then sort
+  const filteredList = list
+    .filter((item) => typeof item === "number")
+    .toSorted((a, b) => a - b);
+
+  if (filteredList.length === 0) {
+    return null;
+  }
+  // if odd length, just return the middle index
+  // else return the sum of the two middle indices divided by 2
+  if (filteredList.length % 2) {
+    const middleIndex = Math.floor(filteredList.length / 2);
+    return filteredList[middleIndex];
+  } else {
+    const secondIndex = filteredList.length / 2;
+    const firstIndex = secondIndex - 1;
+    const median = (filteredList[firstIndex] + filteredList[secondIndex]) / 2;
+    // console.log(median);
+    return median;
+  }
 }
 
+calculateMedian([6, -2, 2, 12, 14]);
 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 +35,17 @@ 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 +1,16 @@
-function dedupe() {}
+function dedupe(arr) {
+  const placeholder = [];
+
+  if (arr.length === 0) {
+    return arr;
+  }
+
+  arr.forEach((element) => {
+    if (!placeholder.includes(element)) {
+      placeholder.push(element);
+    }
+  });
+
+  return placeholder;
+}
+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 empty array, returns 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("array with no duplicates returns copy of original", () => {
+  expect(dedupe([1, 3, 4])).toEqual([1, 3, 4]);
+});
 
 // 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("removes duplicates, while preserving first occurrance of each element", () => {
+  const inputArr = [1, 3, 3, "as", "as", "df"];
+  expect(dedupe(inputArr)).toEqual([1, 3, "as", "df"]);
+  expect(dedupe(inputArr)).not.toBe(inputArr);
+});
+
+// Given an array where all elements are the same
+// When passed to the dedupe function
+// Then it should return an array with that single element
+test("when all items are same, return array containing one single one of that item", () => {});
+expect(dedupe(["a", "a", "a", "a"])).toEqual(["a"]);

Sprint-1/implement/max.js

@@ -1,4 +1,16 @@
-function findMax(elements) {
+function findMax(nums) {
+  if (!Array.isArray(nums)) {
+    throw new TypeError("Expected an array");
+  }
+
+  return nums.reduce((acc, curr) => {
+    // ignores non-num values
+    if (typeof curr !== "number" || isNaN(curr)) {
+      return acc;
+    }
+
+    return curr > acc ? curr : acc;
+  }, -Infinity); // returns -Infinity for empty elements arr, as reduce callback never runs.
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -1,9 +1,11 @@
 /* Find the maximum element of an array of numbers
 
-In this kata, you will need to implement a function that find the largest numerical element of an array.
+In this kata, you will need to implement a function that find the 
+largest numerical element of an array.
 
 E.g. max([30, 50, 10, 40]), target output: 50
-E.g. max(['hey', 10, 'hi', 60, 10]), target output: 60 (sum ignores any non-numerical elements)
+E.g. max(['hey', 10, 'hi', 60, 10]), 
+target output: 60 (sum ignores any non-numerical elements)
 
 You should implement this function in max.js, and add tests for it in this file.
 
@@ -16,28 +18,48 @@ 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("empty array returns -Infinity", () => {
+  expect(findMax([])).toEqual(-Infinity);
+});
 
 // Given an array with one number
 // When passed to the max function
 // Then it should return that number
+test("array with single element returns that element", () => {
+  expect(findMax([3])).toEqual(3);
+});
 
 // Given an array with both positive and negative numbers
 // When passed to the max function
 // Then it should return the largest number overall
+test("array with positive and negative elements still returns correct value", () => {
+  expect(findMax([-3, 3])).toEqual(3);
+});
 
 // Given an array with just negative numbers
 // When passed to the max function
 // Then it should return the closest one to zero
+test("array of all negative numbers returns closest value to zero", () => {
+  expect(findMax([-5, -6, -3, -12])).toEqual(-3);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+test("array of decimal numbers returns correct value", () => {
+  expect(findMax([3.3, 12.2, 4.3, 22.22])).toEqual(22.22);
+});
 
 // 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("ignores non-numeric values in array and returns max", () => {
+  expect(findMax([3, "asd", [22], { a: 12 }, 12])).toEqual(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("if all elements are non-numeric, return -Infinity", () => {
+  expect(findMax(["67", "asd", [22], { a: 12 }, "ss"])).toEqual(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,10 @@
 function sum(elements) {
+  return elements.reduce((acc, curr) => {
+    if (typeof curr !== "number" || isNaN(curr)) {
+      return acc;
+    }
+    return acc + curr;
+  }, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,37 @@ 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("empty array should return 0", () => expect(sum([])).toEqual(0));
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
+test("array of single value should return that value", () =>
+  expect(sum([3])).toEqual(3));
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+test("should return correct sum for negative and positive numbers", () =>
+  expect(sum([-2, -4, 6])).toEqual(0));
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
 
+// use toBeCloseTo to account for floating point
+test("should sum floats", () => expect(sum([0.1, 0.2])).toBeCloseTo(0.3));
+
 // 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("ignores non-numerical values in array", () => {
+  expect(sum(["asd", { a: 12 }, [22, 33], 3, 3])).toEqual(6);
+});
 
 // 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("array of all non-numbers should return 0", () => {
+  expect(sum(["asdf", { a: 12 }, [22, 33]])).toEqual(0);
+});