Coursework/sprint 3/reading list

Sprint-1/fix/median.js

@@ -5,10 +5,33 @@
 // 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;
+//}
+
+//module.exports = calculateMedian;
+
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  const numbers = list.filter((item) => typeof item === "number");
+
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  const sorted = [...numbers].sort((a, b) => a - b);
+  const middleIndex = Math.floor(sorted.length / 2);
+
+  if (sorted.length % 2 !== 0) {
+    return sorted[middleIndex];
+  }
+
+  return (sorted[middleIndex - 1] + sorted[middleIndex]) / 2;
 }
 
 module.exports = calculateMedian;

Sprint-1/fix/median.test.js

@@ -48,3 +48,4 @@ describe("calculateMedian", () => {
     it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
   );
 });
+

Sprint-1/implement/dedupe.js

@@ -1 +1,20 @@
-function dedupe() {}
+//function dedupe() {}
+
+function dedupe(array) {
+  if (!Array.isArray(array)) return [];
+
+  const result = [];
+  const seen = new Set();
+
+  for (const item of array) {
+    if (!seen.has(item)) {
+      seen.add(item);
+      result.push(item);
+    }
+  }
+
+  return result;
+}
+
+module.exports = dedupe;
+

Sprint-1/implement/dedupe.test.js

@@ -25,3 +25,4 @@ test.todo("given an empty array, it returns an empty 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
+

Sprint-1/implement/max.js

@@ -1,4 +1,20 @@
+//function findMax(elements) {
+//}
+
+//module.exports = findMax;
+
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    return -Infinity;
+  }
+
+  const numbers = elements.filter(item => typeof item === "number");
+
+  if (numbers.length === 0) {
+    return -Infinity;
+  }
+
+  return Math.max(...numbers);
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -41,3 +41,4 @@ test.todo("given an empty array, returns -Infinity");
 // 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
+

Sprint-1/implement/sum.js

@@ -1,4 +1,22 @@
+//function sum(elements) {
+//}
+
+//module.exports = sum;
+
 function sum(elements) {
+  if (!Array.isArray(elements)) {
+    return 0;
+  }
+
+  let total = 0;
+
+  for (const item of elements) {
+    if (typeof item === "number") {
+      total += item;
+    }
+  }
+
+  return total;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -34,3 +34,4 @@ test.todo("given an empty array, returns 0")
 // 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
+

Sprint-1/refactor/includes.js

@@ -1,8 +1,19 @@
 // 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;
+//}
+
+//module.exports = includes;
+
 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;
     }

Sprint-1/refactor/includes.test.js

@@ -36,3 +36,5 @@ test("searches for null", () => {
 
   expect(currentOutput).toEqual(targetOutput);
 });
+
+

Sprint-2/debug/address.js

@@ -12,4 +12,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address.houseNumber}`);

Sprint-2/debug/author.js

@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
-}
+for (const key in author) {
+  console.log(author[key]);
+}

Sprint-2/debug/recipe.js

@@ -10,6 +10,9 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+console.log(`${recipe.title} serves ${recipe.serves}`);
+
+for (const ingredient of recipe.ingredients) {
+  console.log(ingredient);
+}
+

Sprint-2/implement/contains.js

@@ -1,3 +1,14 @@
-function contains() {}
+//function contains() {}
+
+//module.exports = contains;
+
+function contains(obj, prop) {
+
+  if (obj === null || typeof obj !== "object" || Array.isArray(obj)) {
+    return false;
+  }
+
+  return prop in obj;
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -1,35 +1,20 @@
 const contains = require("./contains.js");
 
-/*
-Implement a function called contains that checks an object contains a
-particular property
+test("contains on empty object returns false", () => {
+  expect(contains({}, "a")).toBe(false);
+});
 
-E.g. contains({a: 1, b: 2}, 'a') // returns true
-as the object contains a key of 'a'
+test("returns true when object contains the property", () => {
+  expect(contains({ a: 1, b: 2 }, "a")).toBe(true);
+});
 
-E.g. contains({a: 1, b: 2}, 'c') // returns false
-as the object doesn't contains a key of 'c'
-*/
+test("returns false when object does not contain the property", () => {
+  expect(contains({ a: 1, b: 2 }, "c")).toBe(false);
+});
 
-// Acceptance criteria:
+test("returns false for invalid input like an array", () => {
+  expect(contains([1, 2, 3], "0")).toBe(false);
+  expect(contains(null, "a")).toBe(false);
+  expect(contains("hello", "length")).toBe(false);
+});
 
-// Given a contains function
-// When passed an object and a property name
-// Then it should return true if the object contains the property, false otherwise
-
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error

Sprint-2/implement/lookup.js

@@ -1,5 +1,22 @@
-function createLookup() {
-  // implementation here
+
+function createLookup(countryCurrencyPairs) {
+
+  if (!Array.isArray(countryCurrencyPairs)) return {};
+
+  const lookup = {};
+
+  for (const pair of countryCurrencyPairs) {
+
+    if (!Array.isArray(pair) || pair.length < 2) continue;
+
+    const [countryCode, currencyCode] = pair;
+
+    if (typeof countryCode !== "string" || typeof currencyCode !== "string") continue;
+
+    lookup[countryCode] = currencyCode;
+  }
+
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,35 +1,37 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
-
-/*
-
-Create a lookup object of key value pairs from an array of code pairs
-
-Acceptance Criteria:
-
-Given
- - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
-
-When
- - createLookup function is called with the country-currency array as an argument
-
-Then
- - It should return an object where:
- - The keys are the country codes
- - The values are the corresponding currency codes
-
-Example
-Given: [['US', 'USD'], ['CA', 'CAD']]
-
-When
-createLookup(countryCurrencyPairs) is called
-
-Then
-It should return:
- {
-   'US': 'USD',
-   'CA': 'CAD'
- }
-*/
+test("creates a lookup object from country/currency pairs", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  expect(createLookup(input)).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
+
+test("returns empty object for empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+test("ignores invalid pairs", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA"],
+    "bad",            
+    ["DE", "EUR"],
+  ];
+
+  expect(createLookup(input)).toEqual({
+    US: "USD",
+    DE: "EUR",
+  });
+});
+
+test("returns empty object for invalid input", () => {
+  expect(createLookup(null)).toEqual({});
+  expect(createLookup("hello")).toEqual({});
+  expect(createLookup({})).toEqual({});
+});

Sprint-2/implement/querystring.js

@@ -14,3 +14,4 @@ function parseQueryString(queryString) {
 }
 
 module.exports = parseQueryString;
+

Sprint-2/implement/querystring.test.js

@@ -1,12 +1,19 @@
-// In the prep, we implemented a function to parse query strings.
-// Unfortunately, it contains several bugs!
-// Below is one test case for an edge case the implementation doesn't handle well.
-// Fix the implementation for this test, and try to think of as many other edge cases as possible - write tests and fix those too.
+const parseQueryString = require("./querystring.js");
 
-const parseQueryString = require("./querystring.js")
+test("parses a single key-value pair", () => {
+  expect(parseQueryString("fruit=banana")).toEqual({
+    fruit: "banana",
+  });
+});
 
-test("parses querystring values containing =", () => {
-  expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+test("parses multiple key-value pairs", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({
+    a: "1",
+    b: "2",
   });
 });
+
+test("returns empty object for empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+