London | 26-ITP-May | Edina Kurdi | Sprint 1 | coursework-Data-Groups

Sprint-1/fix/median.js

@@ -6,9 +6,39 @@
 // 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;
+  //check if the input is an array
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  //check if list consists of numbers
+  list = list.filter((item) => typeof item === "number" && !isNaN(item));
+
+  //if nothing remained in the updated list, it was non-numbers, so that should return null
+
+  if (list.length === 0) return null;
+
+  //sort a copy of the array
+  const listCopy = Array.from(list);
+  const sortedList = listCopy.sort((a, b) => a - b);
+
+  //find the position of the median
+  let medianPosition = (list.length + 1) / 2 - 1;
+
+  //if integer, that will be an exact position
+  if (medianPosition % 1 === 0) {
+    let median = sortedList[medianPosition];
+    return median;
+  } else {
+    // if not a whole number, we need to average the 2 middle numbers
+    let mid1 = Math.floor((list.length + 1) / 2) - 1;
+    let mid2 = Math.floor((list.length + 1) / 2);
+
+    median = 0.5 * (sortedList[mid1] + sortedList[mid2]);
+    return median;
+  }
 }
 
+// console.log(calculateMedian([1, 2, 3, 4, 5, 6, 7, 8]));
+
 module.exports = calculateMedian;

Sprint-1/implement/dedupe.js

@@ -1 +1,17 @@
-function dedupe() {}
+function dedupe(array) {
+  //create a duplicate,to avoid changing the array
+  const copiedArray = Array.from(array);
+
+  //Initialise an empty array (to collect non-duplicates in)
+  const dedupedArray = [];
+
+  //create a for loop to collect non-duplicates
+  for (element of copiedArray) {
+    if (!dedupedArray.includes(element)) {
+      dedupedArray.push(element);
+    }
+  }
+  return dedupedArray;
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -16,13 +16,21 @@ 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("should return an empty array for 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
+test("should return the original array, if all elements are unique in it", () => {
+  expect(dedupe([4, 5, "hello"])).toEqual([4, 5, "hello"]);
+});
 
 // 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("should return same elements, same order, but duplicates removed for an array with duplicates", () => {
+  expect(dedupe(["a", "a", 3, "b", 3, "b", "c"])).toEqual(["a", 3, "b", "c"]);
+});

Sprint-1/implement/max.js

@@ -1,4 +1,10 @@
 function findMax(elements) {
+  // filter out non-number items from elements
+  elements = elements.filter((element) => typeof element === "number");
+
+  // find maximum
+  const max = Math.max(...elements);
+  return max;
 }
 
 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("should return -Infinity for an empty array", () => {
+  expect(findMax([])).toEqual(-Infinity);
+});
 
 // Given an array with one number
 // When passed to the max function
 // Then it should return that number
+test("should return the number when array contains one number ", () => {
+  expect(findMax([5])).toEqual(5);
+});
 
 // Given an array with both positive and negative numbers
 // When passed to the max function
 // Then it should return the largest number overall
+test("should return the largest number when passed negative and positive numbers", () => {
+  expect(findMax([-5, 5, -2, 2])).toEqual(5);
+});
 
 // Given an array with just negative numbers
 // When passed to the max function
 // Then it should return the closest one to zero
+test("should return the number closest to 0, when the numbers are all negative in the array", () => {
+  expect(findMax([-5, -3, -1, -9])).toEqual(-1);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+test("should return the largest number among decimals", () => {
+  expect(findMax([2.3, 1.6, 9.4, 11.25])).toEqual(11.25);
+});
 
 // 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("should ignore non-numeric values, and calculate the max of the numbers", () => {
+  expect(findMax(["all", null, true, [2, 3], 3, 7])).toEqual(7);
+});
 
 // 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("should return undefined if all the elements are non-numbers", () => {
+  expect(findMax(["nope", null, []])).toEqual(-Infinity);
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,17 @@
 function sum(elements) {
+  //filter out non-numbers
+  elements = elements.filter((element) => typeof element === "number");
+
+  // initialise a sum total
+  total = 0;
+
+  // loop through the elements of the array and add each to the total
+  for (let i = 0; i < elements.length; i++) {
+    total = total + elements[i];
+  }
+
+  // finally return the total
+  return total;
 }
 
 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("should return 0 for an empty array", () => {
+  expect(sum([])).toEqual(0);
+});
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
+test("should return the number for an array of that single number", () => {
+  expect(sum([5])).toEqual(5);
+});
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+test("should return the correct sum even with negative numbers in the array", () => {
+  expect(sum([-5, -2, -3, 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("should correctly sum an array containing decimals", () => {
+  expect(sum([2.3, 2.7])).toEqual(5);
+});
 
 // 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("should ignore non-numbers and calculate the sum of the numbers in the array", () => {
+  expect(sum([null, "", 5, 7, true, "ten"])).toEqual(12);
+});
 
 // 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("should return 0 for only non-number inputs", () => {
+  expect(sum([null, "", true, "ten"])).toEqual(0);
+});

Sprint-1/refactor/includes.js

@@ -1,13 +1,21 @@
 // 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];
+//     if (element === target) {
+//       return true;
+//     }
+//   }
+//   return false;
+// }
+
 function includes(list, target) {
-  for (let index = 0; index < list.length; index++) {
-    const element = list[index];
+  for (element of list) {
     if (element === target) {
       return true;
     }
   }
   return false;
 }
-
 module.exports = includes;