Glasgow | ITP May 25 | Mirabelle Morah | Data groups | Sprint 1

Sprint-1/fix/median.js

@@ -5,10 +5,39 @@
 // 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 median;
+// }
+
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  // This checks if the input is not an array
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  //  This checks if the input is not an a number (keep only numbers)
+  const numericValues = list.filter(val => typeof val === 'number' && !isNaN(val));
+
+  // If no numeric values found, return null
+  if (numericValues.length === 0) {
+    return null;
+  }
+
+  // This sorts the numeric values and does not change original array
+  const sortedNumbers = numericValues.sort((a, b) => a - b);
+
+  const length = sortedNumbers.length;
+  const middleIndex = Math.floor(length / 2);
+
+  // This checks that if there are odd number of elements, return the middle element
+  if (length % 2 === 1) {
+    return sortedNumbers[middleIndex];
+  }
+
+  // If even number of elements, this returns the average of the two middle elements
+  return (sortedNumbers[middleIndex - 1] + sortedNumbers[middleIndex]) / 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 +35,17 @@ 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 +1,8 @@
-function dedupe() {}
+function dedupe(list) {
+  return [...new Set(list)];
+}
+console.log(dedupe(['a','a','b','c','c'])); // returns ['a', 'b', 'c']
+console.log(dedupe([5, 1, 1, 2, 3, 2, 5, 8])); // returns [5, 1, 2, 3, 8]
+console.log(dedupe([])); // returns []
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,12 +16,33 @@ E.g. dedupe([1, 2, 1]) target output: [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");
+describe("dedupe", () => {
+  it("should return an empty array when given 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
+  // When passed to the dedupe function
+  // Then it should return a copy of the original array
 
-// Given an array with strings or numbers
-// When passed to the dedupe function
-// Then it should remove the duplicate values, preserving the first occurence of each element
+  it("should return a copy of the original array when given an array with no duplicates", () => {
+    const arr = [1, 2, 3];
+    expect(dedupe(arr)).toEqual([1, 2, 3]);
+    // Also check it's not the same reference
+    expect(dedupe(arr)).not.toBe(arr);
+  });
+
+  // Given an array with strings or numbers
+  // When passed to the dedupe function
+  // Then it should remove the duplicate values, preserving the first occurence of each element
+
+  it("should remove duplicates of an array with strings and preserve first occurrence", () => {
+    expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+  });
+});
+
+describe("dedupe", () => {
+  it("should work with mixed types and remove duplicates (numbers and strings)", () => {
+    expect(dedupe([1, "1", 2, "2", 1, "1"])).toEqual([1, "1", 2, "2"]);
+  });
+});

Sprint-1/implement/max.js

@@ -1,4 +1,22 @@
 function findMax(elements) {
+  // Makes a new list called elementFinder that only keeps items from elements
+  // that are real numbers (not words, not NaN)
+  const elementFinder = elements.filter(
+    (el) => typeof el === "number" && !isNaN(el)
+  );
+
+  // If there are no numbers in the list, return -Infinity (which means “no biggest number”).
+  if (elementFinder.length === 0) {
+    return -Infinity;
+  }
+
+  // Otherwise, return the biggest number from elementFinder.
+  return Math.max(...elementFinder);
 }
 
+console.log(findMax([1, 2, 20, 4, 5]));
+console.log(findMax([1, "2", 3, "four", 5]));
+console.log(findMax([NaN, null, 5, 10, "abc"]));
+console.log(findMax([NaN, null, "5", "10", "abc"]));
+
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -15,29 +15,48 @@ 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([])).toEqual(-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, "baby"])).toEqual(42);
+});
 
 // 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 the largest", () => {
+  expect(findMax([-10, 5, 20, -30, 0])).toEqual(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 an array with only negative numbers, returns the closest to zero", () => {
+  expect(findMax([-100, -50, -1, -20])).toEqual(-1);
+});
 
 // 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 the largest decimal", () => {
+  expect(findMax([1.5, 2.7, 0.3, 2.6])).toEqual(2.7);
+});
 
 // 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 an array with non-number values, returns the max of numbers only", () => {
+  expect(findMax([1, "2", 3, "four", 5])).toEqual(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
+test("given an array with only non-number values, returns -Infinity", () => {
+  expect(findMax(["a", "b", "c", null, undefined])).toEqual(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,21 @@
-function sum(elements) {
+function sum(list) {
+    // Remember this filters the list to only include numbers and ignore strings or other types
+    const filterList = list.filter(
+        (el) => typeof el === "number" && !isNaN(el)
+    );
+
+    // If there are no numbers, return 0
+    if (filterList.length === 0) {
+        return 0;
+    }
+    // If the sum is negative, return 0; otherwise, return the sum
+    const total = filterList.reduce((acc, curr) => acc + curr, 0);
+    return total;
 }
 
+console.log(sum([10, 20, 30])); // 60
+console.log(sum(['hey', 10, 'hi', 60, 10])); // 80
+console.log(sum([])); // 0
+console.log(sum([-10, -20, 30])); // 0
+
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,42 @@ 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([])).toEqual(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])).toEqual(42);
+});
 
 // 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 correct sum", () => {
+  expect(sum([-10, -20, -30])).toEqual(-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 correct sum", () => {
+  expect(sum([1.5, 2.5, 3])).toEqual(7);
+});
 
 // 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 an array with non-number values, returns sum of numbers only", () => {
+  expect(sum([1, "2", 3, "four", 5])).toEqual(9);
+});
 
 // 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", null, undefined])).toEqual(0);
+});