London | 26-ITP-Sep| Mahdi Rafiei | Sprint 1 | Sprint1 exercises

Sprint-1/fix/median.js

@@ -1,14 +1,50 @@
-// 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
+// median.test.js
 
-// Hint: Please consider scenarios when 'list' isn't an array, is empty,
-// or contains values that aren't numbers (the function is expected to throw - see the tests).
+// Someone has implemented calculateMedian but it isn't
+// passing all the tests...
+// Fix the implementation of calculateMedian so it passes all tests
 
-function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
-}
+const calculateMedian = require("./median.js");
 
-module.exports = calculateMedian;
+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))
+  );
+});

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 +16,9 @@ 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

Sprint-1/implement/describe-median.js

@@ -20,6 +20,13 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  try {
+    const median = calculateMedian(list);
+    return `The median is ${median}`;
+  } catch (error) {
+    return `Could not calculate a median: ${error.message}`;
+  }
+}
 
 module.exports = describeMedian;

Sprint-1/implement/describe-median.test.js

@@ -20,13 +20,24 @@ const describeMedian = require("./describe-median.js");
 // Given an array of numbers
 // When passed to describeMedian
 // Then it should return "The median is " followed by the median
-// Delete this test.todo and replace it with a test.
-test.todo('given [1, 2, 3], returns "The median is 2"');
+test('given [1, 2, 3], returns "The median is 2"', () => {
+  expect(describeMedian([1, 2, 3])).toBe("The median is 2");
+});
 
 // Given an empty array
 // When passed to describeMedian
 // Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
+test("given an empty array, returns an error message", () => {
+  expect(describeMedian([])).toBe(
+    "Could not calculate a median: calculateMedian requires a non-empty array"
+  );
+});
 
 // Given something that isn't an array of numbers, e.g. "banana"
 // When passed to describeMedian
 // Then it should return "Could not calculate a median: calculateMedian requires an array of numbers"
+test('given "banana", returns an error message', () => {
+  expect(describeMedian("banana")).toBe(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+});

Sprint-1/implement/max.js

@@ -1,4 +1,17 @@
 function findMax(elements) {
+  const numbers = elements.filter((item) => typeof item === "number");
+  if (numbers.length === 0) {
+    return -Infinity;
+  }
+  let max = -Infinity;
+
+  for (const num of numbers) {
+    if (num > max) {
+      max = num;
+    }
+  }
+
+  return max;
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -3,7 +3,7 @@
 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]) throws Error("findMax requires an array of numbers") (max can't compare non-numerical elements, so it shouldn't guess)
+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.
 
@@ -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([])).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([42])).toBe(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, 3, -2])).toBe(5);
+});
 
 // 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([-10, -3, -20])).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 the largest decimal", () => {
+  expect(findMax([1.2, 3.5, 2.8])).toBe(3.5);
+});
 
-// Given an array containing a value that isn't a number
+// Given an array with non-number values
 // When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
+// Then it should return the max and ignore non-numeric values
+test("given an array with non-number values, ignores them and returns the max", () => {
+  expect(findMax(['hey', 10, 'hi', 60, 10])).toBe(60);
+});
 
-// Given something that isn't an array at all, such as "hey", 42 or no argument
+// Given an array with only non-number values
 // When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
+// 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', null, undefined])).toBe(-Infinity);
+});

Sprint-1/implement/mean.js

@@ -1,3 +1,17 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+  for (const item of list) {
+    if (typeof item !== "number") {
+      throw new Error("calculateMean requires an array of numbers");
+    }
+  }
+  const total = list.reduce((sum, number) => sum + number, 0);
+  return total / list.length;
+}
 
 module.exports = calculateMean;

Sprint-1/implement/mean.test.js

@@ -22,29 +22,68 @@ const calculateMean = require("./mean.js");
 // Given an array of numbers
 // When passed to calculateMean
 // Then it should return their mean
-// Delete this test.todo and replace it with a test.
-test.todo("given [1, 2, 6], returns 3");
+test("given [1, 2, 6], returns 3", () => {
+  expect(calculateMean([1, 2, 6])).toBe(3);
+});
 
 // Given an array with a single number
 // When passed to calculateMean
 // Then it should return that number
+test("given [5], returns 5", () => {
+  expect(calculateMean([5])).toBe(5);
+});
 
 // Given an array containing negative or decimal numbers
 // When passed to calculateMean
 // Then it should return the correct mean
+test("given negative and decimal numbers, returns the correct mean", () => {
+  expect(calculateMean([-2.5, 1.5, 4])).toBe(1);
+});
 
 // Given an empty array
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires a non-empty array")
+test("given an empty array, throws the correct error", () => {
+  expect(() => calculateMean([])).toThrow(
+    "calculateMean requires a non-empty array"
+  );
+});
 
 // Given a value that isn't an array, e.g. "banana", 42, null or {}
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+test("given a non-array value, throws the correct error", () => {
+  expect(() => calculateMean("banana")).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+
+  expect(() => calculateMean(42)).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+
+  expect(() => calculateMean(null)).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+
+  expect(() => calculateMean({})).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
 
 // Given no argument at all
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+test("given no argument, throws the correct error", () => {
+  expect(() => calculateMean()).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
 
 // Given an array containing a non-number value, e.g. [1, "2", 3]
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+test("given an array containing a non-number, throws the correct error", () => {
+  expect(() => calculateMean([1, "2", 3])).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,9 @@
 function sum(elements) {
+  const numbers = elements.filter((item) => typeof item === "number");
+  if (numbers.length === 0) {
+    return 0;
+  }
+  return numbers.reduce((total, num) => total + num, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -3,7 +3,7 @@
 In this kata, you will need to implement a function that sums the numerical elements of an array
 
 E.g. sum([10, 20, 30]), target output: 60
-E.g. sum(['hey', 10, 'hi', 60, 10]) throws Error("sum requires an array of numbers") (sum can't add non-numerical elements, so it shouldn't guess)
+E.g. sum(['hey', 10, 'hi', 60, 10]), target output: 80 (ignore any non-numerical elements)
 */
 
 const sum = require("./sum.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.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 that number", () => {
+  expect(sum([42])).toBe(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 the correct total", () => {
+  expect(sum([-5, 10, -3])).toBe(2);
+});
 
 // 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 the correct total", () => {
+  expect(sum([1.5, 2.5, 3.1])).toBe(7.1);
+});
 
-// Given an array containing a value that isn't a number
+// Given an array containing non-number values
 // When passed to the sum function
-// Then it should throw Error("sum requires an array of numbers")
+// Then it should ignore the non-numerical values and return the sum of the numerical elements
+test("given an array with non-number values, ignores them and returns the sum of numbers", () => {
+  expect(sum(["hey", 10, "hi", 60, 10])).toBe(80);
+});
 
-// Given something that isn't an array at all, such as "hey", 42 or no argument
+// Given an array with only non-number values
 // When passed to the sum function
-// Then it should throw Error("sum requires an array of numbers")
+// 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", null, undefined, "b"])).toBe(0);
+});

Sprint-1/refactor/includes.js

@@ -1,8 +1,7 @@
 // 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];
+  for (const element of list) {
     if (element === target) {
       return true;
     }