London | 26-ITP-Jan | Miriam Jorna | Sprint 1 | Data Groups

Sprint-1/fix/median.js

@@ -1,3 +1,4 @@
+
 // Fix this implementation
 // Start by running the tests for this function
 // If you're in the Sprint-1 directory, you can run `npm test -- fix` to run the tests in the fix directory
@@ -6,9 +7,25 @@
 // 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;
+  // filter only numbers from the list
+  const numbers = list.filter(item => typeof item === "number");
+
+  // return null if no numbers found
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // sort the numbers
+  numbers.sort((a, b) => a - b);
+
+  const middleIndex = Math.floor(numbers.length / 2);
+
+  // if even number of elements, average the two middle values
+  if (numbers.length % 2 === 0) {
+    return (numbers[middleIndex - 1] + numbers[middleIndex]) / 2;
+  }
+
+  return numbers[middleIndex];
 }
 
 module.exports = calculateMedian;

Sprint-1/fix/median.test.js

@@ -4,47 +4,31 @@
 // passing all the tests...
 // Fix the implementation of calculateMedian so it passes all tests
 
-const calculateMedian = require("./median.js");
-
-describe("calculateMedian", () => {
-  [
-    { input: [1, 2, 3], expected: 2 },
-    { input: [1, 2, 3, 4, 5], expected: 3 },
-    { 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 [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
-  );
-
-  [
-    { input: [3, 1, 2], expected: 2 },
-    { input: [5, 1, 3, 4, 2], expected: 3 },
-    { input: [4, 2, 1, 3], expected: 2.5 },
-    { input: [6, 1, 5, 3, 2, 4], expected: 3.5 },
-    { input: [110, 20, 0], expected: 20 },
-    { input: [6, -2, 2, 12, 14], expected: 6 },
-  ].forEach(({ input, expected }) =>
-    it(`returns the correct median for unsorted array [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
-  );
-
-  it("doesn't modify the input array [3, 1, 2]", () => {
-    const list = [3, 1, 2];
-    calculateMedian(list);
-    expect(list).toEqual([3, 1, 2]);
-  });
-
-  [ 'not an array', 123, null, undefined, {}, [], ["apple", null, undefined] ].forEach(val =>
-    it(`returns null for non-numeric array (${val})`, () => expect(calculateMedian(val)).toBe(null))
-  );
-
-  [
-    { input: [1, 2, "3", null, undefined, 4], expected: 2 },
-    { input: ["apple", 1, 2, 3, "banana", 4], expected: 2.5 },
-    { input: [1, "2", 3, "4", 5], expected: 3 },
-    { input: [1, "apple", 2, null, 3, undefined, 4], expected: 2.5 },
-    { input: [3, "apple", 1, null, 2, undefined, 4], expected: 2.5 },
-    { input: ["banana", 5, 3, "apple", 1, 4, 2], expected: 3 },
-  ].forEach(({ input, expected }) =>
-    it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
-  );
-});
+function calculateMedian(list) {
+  // return null if input is not an array
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  // filter only numbers, using a copy to avoid modifying the original
+  const numbers = list.filter(item => typeof item === "number");
+
+  // return null if no numbers found
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // sort the numbers
+  numbers.sort((a, b) => a - b);
+
+  const middleIndex = Math.floor(numbers.length / 2);
+
+  // if even number of elements, average the two middle values
+  if (numbers.length % 2 === 0) {
+    return (numbers[middleIndex - 1] + numbers[middleIndex]) / 2;
+  }
+
+  return numbers[middleIndex];
+}
+
+module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,5 @@
-function dedupe() {}
+function dedupe(arr) {
+  return [...new Set(arr)];
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,7 +16,22 @@ 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([]);
+});
+
+test("given an array with no duplicates, it returns a copy of the original array", () => {
+  expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+});
+
+test("given an array of numbers with duplicates, it returns array with duplicates removed", () => {
+  expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+});
+
+test("given an array of strings with duplicates, it returns array with duplicates removed", () => {
+  expect(dedupe(['a', 'a', 'a', 'b', 'b', 'c'])).toEqual(['a', 'b', 'c']);
+});
 
 // Given an array with no duplicates
 // When passed to the dedupe function

Sprint-1/implement/max.js

@@ -1,4 +1,6 @@
-function findMax(elements) {
+function findMax(arr) {
+  const numbers = arr.filter(item => typeof item === "number");
+  return Math.max(...numbers);
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -12,11 +12,33 @@ 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");
+test("given an empty array, returns -Infinity", () => {
+  expect(findMax([])).toEqual(-Infinity);
+});
+
+test("given an array with one number, returns that number", () => {
+  expect(findMax([5])).toEqual(5);
+});
+
+test("given an array with positive and negative numbers, returns the largest", () => {
+  expect(findMax([30, -10, 50, -40])).toEqual(50);
+});
+
+test("given an array with just negative numbers, returns the closest to zero", () => {
+  expect(findMax([-5, -1, -10])).toEqual(-1);
+});
+
+test("given an array with decimal numbers, returns the largest decimal", () => {
+  expect(findMax([1.5, 2.7, 0.3])).toEqual(2.7);
+});
+
+test("given an array with non-number values, returns the max and ignores non-numeric values", () => {
+  expect(findMax(['hey', 10, 'hi', 60, 10])).toEqual(60);
+});
+
+test("given an array with only non-number values, returns -Infinity", () => {
+  expect(findMax(['hey', 'hi'])).toEqual(-Infinity);
+});
 
 // Given an array with one number
 // When passed to the max function

Sprint-1/implement/sum.js

@@ -1,4 +1,7 @@
-function sum(elements) {
+function sum(arr) {
+  return arr
+    .filter(item => typeof item === "number")
+    .reduce((total, num) => total + num, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,28 @@ 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")
+const sum = require("./sum.js");
 
-// Given an array with just one number
-// When passed to the sum function
-// Then it should return that number
+test("given an empty array, returns 0", () => {
+  expect(sum([])).toEqual(0);
+});
 
-// 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 just one number, returns that number", () => {
+  expect(sum([5])).toEqual(5);
+});
 
-// 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 containing negative numbers, returns the correct total sum", () => {
+  expect(sum([10, -5, 20])).toEqual(25);
+});
 
-// 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 decimal numbers, returns the correct total sum", () => {
+  expect(sum([1.5, 2.5, 3.0])).toEqual(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 with non-number values, ignores them and returns sum of numbers", () => {
+  expect(sum(['hey', 10, 'hi', 60, 10])).toEqual(80);
+});
+
+test("given an array with only non-number values, returns 0", () => {
+  expect(sum(['hey', 'hi'])).toEqual(0);
+});

Sprint-1/prep/mean.test.js

@@ -0,0 +1,8 @@
+test("calculates the mean of a list of numbers", () => {
+    const list = [3, 50, 7];
+    const currentOutput = calculateMean(list);
+    const targetOutput = 20;
+
+    expect(currentOutput).toEqual(targetOutput); 
+
+});

Sprint-1/prep/median.test.js

@@ -0,0 +1,14 @@
+test("calculates the the median of a list of odd length", () => {
+    const list = [10, 20, 30, 50, 60];
+    const currentOutput = calculateMedian(list);
+    const targetOutput = 30;
+
+    expect(currentOutput).toEqual(targetOutput);
+});
+
+function calculateMedian(list) {
+  const middleIndex = Math.floor(list.length / 2);
+  const median = list.splice(middleIndex, 1)[0];
+
+  return median;
+}

Sprint-1/prep/middleMean.test.js

@@ -0,0 +1,22 @@
+function calculateMedian(list) {
+    const middleIndex = Math.floor(list.length / 2);
+    const median = list.splice(middleIndex, 1)[0];
+
+    return median;
+}
+
+function calculateMean(list) {
+    const sum = list.reduce((acc, val) => acc + val, 0);
+    const mean = sum / list.length;
+
+    return mean;
+}
+
+const salaries = [10, 20, 30, 40, 60, 80, 80];
+const median = calculateMedian(salaries);
+
+console.log(salaries, "<--- salaries input before we call calculateMean");
+const mean = calculateMean(salaries);
+
+console.log(`The median salary is ${median}`);
+console.log(`The mean salary is ${mean}`);