London | 26-ITP-Sept | Fung Nin Lee | Sprint 1 | Sprint-1 exercise

Sprint-1/fix/median.js

@@ -6,9 +6,29 @@
 // or contains values that aren't numbers (the function is expected to throw - see the tests).
 
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (Array.isArray(list) === false) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  if (list.length === 0) {
+    throw new Error("calculateMedian requires a non-empty array");
+  }
+
+   if (list.some((item) => typeof item === "string" || item === null || item === undefined)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  const sortedList = [...list].sort((a, b) => a - b);
+
+  if (sortedList.length % 2 === 0) {
+    const evenMiddleIndex = sortedList.length / 2;
+    const sumOfEvenMiddleIndex =
+    sortedList[evenMiddleIndex - 1] + sortedList[evenMiddleIndex]
+    return sumOfEvenMiddleIndex / 2;
+  } else {
+    const oddMiddleIndex = Math.floor(sortedList.length / 2);
+    return sortedList[oddMiddleIndex];
+  }
 }
 
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

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

Sprint-1/implement/dedupe.test.js

@@ -1,28 +1,56 @@
 const dedupe = require("./dedupe.js");
-/*
-Dedupe Array
 
-📖 Dedupe means **deduplicate**
+//Dedupe Array
 
-In this kata, you will need to deduplicate the elements of an array
+//📖 Dedupe means **deduplicate**
 
-E.g. dedupe(['a','a','a','b','b','c']) returns ['a','b','c']
-E.g. dedupe([5, 1, 1, 2, 3, 2, 5, 8]) returns [5, 1, 2, 3, 8]
-E.g. dedupe([1, 2, 1]) returns [1, 2]
-*/
+//In this kata, you will need to deduplicate the elements of an array
 
-// Acceptance Criteria:
+describe("dedupe", () => {
+  //E.g. dedupe(['a','a','a','b','b','c']) returns ['a','b','c']
+  it("returns for ['a','a','a','b','b','c']", () => {
+    expect(dedupe(["a", "a", "a", "b", "b", "c"])).toEqual(["a", "b", "c"]);
+  });
 
-// 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");
+  //E.g. dedupe([5, 1, 1, 2, 3, 2, 5, 8]) returns [5, 1, 2, 3, 8]
+  it("returns for [5, 1, 1, 2, 3, 2, 5, 8]", () => {
+    expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+  });
+  //E.g. dedupe([1, 2, 1]) returns [1, 2]
+  //*/
+  it("returns for [1, 2, 1]", () => {
+    expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+  });
 
-// Given an array with no duplicates
-// When passed to the dedupe function
-// Then it should return a copy of the original array
+  // Acceptance Criteria:
 
-// 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 empty array
+  // When passed to the dedupe function
+  // Then it should return an empty array
+
+  it("returns for []", () => {
+    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
+
+  it("returns for [1, 2, 3, 4]", () => {
+    const original = [1, 2, 3, 4];
+    const result = dedupe(original);
+    expect(result).not.toBe(original);
+  });
+
+  // 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.
+  it("returns for ['apple', 'orange', 'banana', 'banana']", () => {
+    expect(dedupe(["apple", "orange", "banana", "banana"])).toEqual([
+      "apple",
+      "orange",
+      "banana",
+    ]);
+  });
+});

Sprint-1/implement/describe-median.js

@@ -1,14 +1,14 @@
 // Don't change this function.
 function calculateMedian(list) {
   if (!Array.isArray(list)) {
-    throw new Error("calculateMedian requires an array of numbers");
+    throw new Error("Could not calculate a median: calculateMedian requires an array of numbers");
   }
   if (list.length === 0) {
-    throw new Error("calculateMedian requires a non-empty array");
+    throw new Error("Could not calculate a median: calculateMedian requires a non-empty array");
   }
   for (const item of list) {
     if (typeof item !== "number") {
-      throw new Error("calculateMedian requires an array of numbers");
+      throw new Error("Could not calculate a median: calculateMedian requires an array of numbers");
     }
   }
   const middleIndex = Math.floor(list.length / 2);
@@ -20,6 +20,9 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  const result = calculateMedian(list);
+  return `The median is ${result}`
+}
 
 module.exports = describeMedian;

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

@@ -21,12 +21,32 @@ const describeMedian = require("./describe-median.js");
 // 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"');
-
-// Given an empty array
-// When passed to describeMedian
-// Then it should return "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"
+describe("describeMedian", () => {
+  it("returns for [1, 2, 3, 4]", () => {
+    const array = [1, 2, 3, 4];
+    const result = describeMedian(array);
+    expect(result).toBe("The median is 2.5");
+  });
+
+  // Given an empty array
+  // When passed to describeMedian
+  // Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
+  it("returns for []", () => {
+    expect(() => describeMedian([])).toThrow(
+      new Error(
+        "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"
+  it("returns for ['banana', 'apple', 'orange']", () => {
+    expect(() => describeMedian(["banana", "apple", "orange"])).toThrow(
+      new Error(
+        "Could not calculate a median: calculateMedian requires an array of numbers"
+      )
+    );
+  });
+});

Sprint-1/implement/max.js

@@ -1,4 +1,10 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+  if (elements.some((element) => typeof element === "string")) {
+    throw new Error("findMax requires an array of numbers");
+  }
+  return Math.max(...elements);
 }
-
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -16,28 +16,72 @@ 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");
+describe("findMax", () => {
+  it("returns for []", () => {
+    expect(findMax([])).toEqual(-Infinity);
+  });
 
-// Given an array with one number
-// When passed to the max function
-// Then it should return that number
+  // Given an array with one number
+  // When passed to the max function
+  // Then it should return that number
+  it("returns for [17]", () => {
+    expect(findMax([17])).toEqual(17);
+  });
 
-// 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 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
+  it("returns for [-6, 15, 30, 42, -90]", () => {
+    expect(findMax([-6, 15, 30, 42, -90])).toEqual(42);
+  });
 
-// Given an array with decimal numbers
-// When passed to the max function
-// Then it should return the largest decimal number
+  // 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 containing a value that isn't a number
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
+  it("returns for [-6, 15, 30, 42, -90]", () => {
+    expect(findMax([-6, 15, 30, 42, -90])).toEqual(42);
+  });
 
-// Given something that isn't an array at all, such as "hey", 42 or no argument
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
+  // Given an array with decimal numbers
+  // When passed to the max function
+  // Then it should return the largest decimal number
+
+  it("returns for [0.5, 1.5, 3.5, 5.5, 7.5]", () => {
+    expect(findMax([0.5, 1.5, 3.5, 5.5, 7.5])).toEqual(7.5);
+  });
+
+  // Given an array containing a value that isn't a number
+  // When passed to the max function
+  // Then it should throw Error("findMax requires an array of numbers")
+
+  it("returns for [2, 4, 'hello', 6, 8, 10]", () => {
+    () =>
+      expect(findMax([2, 4, "hello", 6, 8, 10])).toThrow(
+        new Error("findMax requires an array of numbers")
+      );
+  });
+
+  // Given something that isn't an array at all, such as "hey", 42 or no argument
+  // When passed to the max function
+  // Then it should throw Error("findMax requires an array of numbers")
+
+  it("returns for 'hey'", () => {
+    expect(() => findMax("hey")).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+  });
+
+  it("returns for 42", () => {
+    expect(() => findMax(42)).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+  });
+
+  it("returns for ''", () => {
+    expect(() => findMax()).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+  });
+});

Sprint-1/implement/mean.js

@@ -1,3 +1,24 @@
-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");
+  }
+
+  if (list.some((item) => typeof item === "string")) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+
+  let sum = 0;
+  for (const item of list) {
+    sum += item;
+  }
+
+  const mean = sum / list.length;
+
+  return mean;
+}
 
 module.exports = calculateMean;