London | 26-ITP-January | Mouawia Elkhalifa | Sprint 2 | Data Groups

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) {
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -11,5 +11,5 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:
+${recipe.ingredients.join("\n")}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,10 @@
-function contains() {}
+function contains(obj, prop) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+  }
 
-module.exports = contains;
+  // Use the static Object.hasOwn() method
+  return Object.hasOwn(obj, prop);
+}
+
+module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,16 +20,28 @@ as the object doesn't contains a key of 'c'
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("contains on empty object returns false", () => {
+  expect(contains({}, "a")).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("contains an object with propery  exist, returns true", () => {
+  expect(contains({ a: 1, b: 2 }, "a")).toEqual(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
-
+test("return false when the property does not exist", () => {
+  expect(contains({ a: 1, b: 3 }, "c")).toEqual(false);
+});
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("returns false when input is an array, even if the index exists", () => {
+  // Index 0 exists in this array, but contains() should return false 
+  // because the requirement is for plain objects only.
+  expect(contains(["apple", "banana"], 0)).toEqual(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,13 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  const lookup = {};
+
+  for (const [countryCode, countryCurrency] of countryCurrencyPairs) {
+    lookup[countryCode] = countryCurrency;
+  }
+
+  return lookup;
 }
 
 module.exports = createLookup;
+
+

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,13 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("creates a country currency code lookup for multiple codes",() =>{
+  expect(createLookup([["US", "USD"], ["CA", "CAD"]])).toEqual(
+    {"US":"USD",
+      "CA": "CAD"
+
+  })
+
+})
 
 /*
 

Sprint-2/implement/querystring.js

@@ -1,13 +1,22 @@
 function parseQueryString(queryString) {
+  if (queryString.startsWith("?")) {
+    queryString = queryString.substring(1);
+  }
+
   const queryParams = {};
   if (queryString.length === 0) {
     return queryParams;
   }
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (pair === "") continue;
+
+    const [key, ...valueParts] = pair.split("=");
+    const value = valueParts.join("=");
+
+    queryParams[decodeURIComponent(key)] = decodeURIComponent(value);
   }
 
   return queryParams;

Sprint-2/implement/tally.js

@@ -1,3 +1,19 @@
-function tally() {}
+function tally(arr) {
+  if (!Array.isArray(arr)) {
+    throw new Error("Input must be an array");
+  }
+
+  const result = Object.create(null);
+
+  for (const item of arr) {
+    if (result[item] === undefined) {
+      result[item] = 1;
+    } else {
+      result[item] = result[item] + 1;
+    }
+  }
+
+  return result;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,12 +23,45 @@ const tally = require("./tally.js");
 // Given an empty array
 // When passed to tally
 // Then it should return an empty object
-test.todo("tally on an empty array returns an empty object");
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("tally counts duplicate items correctly", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({
+    a: 2,
+    b: 1,
+    c: 1,
+  });
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("tally throws an error for invalid input", () => {
+  expect(() => tally("hello")).toThrow();
+});
+
+// Given an array containing keys that match built-in object properties
+// When passed to tally
+// Then it should correctly count them without conflicts from inherited properties
+test("tally works correctly with reserved words like toString", () => {
+  const input = ["toString", "toString", "hasOwnProperty"];
+  const expected = {
+    toString: 2,
+    hasOwnProperty: 1,
+  };
+  expect(tally(input)).toEqual(expected);
+});
+
+// Extra verification test to confirm pure object behavior
+test("tally accurately counts prototype method names as strings", () => {
+  const input = ["toString", "toString"];
+  const expected = {
+    toString: 2,
+  };
+  expect(tally(input)).toEqual(expected);
+});

Sprint-2/interpret/invert.js

@@ -1,29 +1,50 @@
-// Let's define how invert should work
+// a) What is the current return value when invert is called with { a : 1 }
+// { key: 1 }
+
+// b) What is the current return value when invert is called with { a: 1, b: 2 }
+// { key: 2 }
+
+// c) What is the target return value when invert is called with { a: 1, b: 2 }
+// { "1": "a", "2": "b" }
 
-// Given an object
-// When invert is passed this object
-// Then it should swap the keys and values in the object
+// d) What does Object.entries return? Why is it needed in this program?
+// It returns an array of [key, value] pairs.
+// It is needed so we can loop through both keys and values at the same time when inverting the object.
 
-// E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
+// e) Explain why the current return value is different from the target output
+// The original code used 'invertedObj.key = value', which creates a property literally named "key"
+// instead of using the value dynamically.
+// This causes each iteration to overwrite the previous one.
+// It also does not handle collisions (multiple keys with the same value).
 
+// f) Fix the implementation of invert (and write tests to prove it's fixed!)
 function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    if (invertedObj[value] === undefined) {
+      invertedObj[value] = key;
+    } else if (Array.isArray(invertedObj[value])) {
+      invertedObj[value].push(key);
+    } else {
+      invertedObj[value] = [invertedObj[value], key];
+    }
   }
 
   return invertedObj;
 }
 
-// a) What is the current return value when invert is called with { a : 1 }
-
-// b) What is the current return value when invert is called with { a: 1, b: 2 }
+// --- CONSOLE TESTS TO PROVE IT IS FIXED ---
+console.log("Test 1 (Simple):", invert({ a: 1 }));
+// Expected: { '1': 'a' }
 
-// c) What is the target return value when invert is called with {a : 1, b: 2}
+console.log("Test 2 (No duplicates):", invert({ x: 10, y: 20 }));
+// Expected: { '10': 'x', '20': 'y' }
 
-// c) What does Object.entries return? Why is it needed in this program?
+console.log("Test 3 (Collision):", invert({ a: 1, b: 1 }));
+// Expected: { '1': ['a', 'b'] }
 
-// d) Explain why the current return value is different from the target output
+console.log("Test 4 (Triple collision):", invert({ a: 1, b: 1, c: 1 }));
+// Expected: { '1': ['a', 'b', 'c'] }
 
-// e) Fix the implementation of invert (and write tests to prove it's fixed!)
+module.exports = invert;