From 28540289c9a86a1dbd3727be350081b9618c1296 Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Mon, 10 Nov 2025 17:11:39 +0000
Subject: [PATCH 01/10] Completed address.js

---
 Sprint-2/debug/address.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..a8fc2386c 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+// I predict that the console will log "My house number is undefined"
+// because it is using array index notation whereas address is an object.
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +15,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address["houseNumber"]}`);

From dd03ab32c9cd198c865acfa099a1a1d392e190d1 Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Mon, 10 Nov 2025 17:22:05 +0000
Subject: [PATCH 02/10] Completed author.js

---
 Sprint-2/debug/author.js | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..8f925b6bb 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,8 +1,14 @@
 // Predict and explain first...
 
+// I predict that the console will log "undefined" because
+// it is looping through elements in a collection (e.g. arrays and sets)
+// whereas author is an object.
+
 // This program attempts to log out all the property values in the object.
 // But it isn't working. Explain why first and then fix the problem
 
+// The loop is trying to loop through an array
+
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +17,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (value in author) {
   console.log(value);
 }

From 00093ebd287b6c5e3fead25ed7763d89e2a420cc Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Tue, 11 Nov 2025 19:36:34 +0000
Subject: [PATCH 03/10] Completed recipe.js

---
 Sprint-2/debug/recipe.js | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..0301114f0 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,5 +1,7 @@
 // Predict and explain first...
 
+// The console will print the recipe title, serves and the recipe object itself rather than the actual ingredient
+
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
 // How can you fix it?
@@ -10,6 +12,8 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+console.log(`titie: ${recipe.title}, serves: ${recipe.serves}, ingredients:\n`);
+
+for (const ingredient of recipe.ingredients) {
+  console.log(ingredient);
+}

From 1e3daf27bc466e0472b0181d9659bb2aa32191ad Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Tue, 11 Nov 2025 20:56:16 +0000
Subject: [PATCH 04/10] Completed contains

---
 Sprint-2/implement/contains.js      |  8 +++++++-
 Sprint-2/implement/contains.test.js | 26 +++++++++++++++++++++++++-
 package.json                        |  8 ++++++++
 3 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 package.json

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..d1a5a25f5 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,9 @@
-function contains() {}
+function contains(object, property) {
+  if (object === null || typeof object !== "object" || Array.isArray(object)) {
+    throw new Error("object is not an object type!");
+  }
+
+  return Object.prototype.hasOwnProperty.call(object, property);
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..bb7efbcf1 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -16,20 +16,44 @@ as the object doesn't contains a key of 'c'
 // 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
+test("object contains the property returns true", () => {
+  const object = { forename: "John" };
+  expect(contains(object, "forename")).toEqual(true);
+  expect(contains(object, "surname")).toEqual(false);
+});
 
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("empty object returns false", () => {
+  const object = {};
+  const result = contains(object);
+  expect(result).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("object contains properties returns true for a property", () => {
+  const object = { forename: "John", surname: "Appleseed" };
+  const property = "surname";
+  const result = contains(object, property);
+  expect(result).toEqual(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("object returns false for a non-existent property", () => {
+  const object = { forename: "John", surname: "Appleseed" };
+  const property = "middlename";
+  const result = contains(object, property);
+  expect(result).toEqual(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("object throws an error for a non-object type", () => {
+  expect(() => contains([])).toThrow("object is not an object type!");
+});
diff --git a/package.json b/package.json
new file mode 100644
index 000000000..37e34c85a
--- /dev/null
+++ b/package.json
@@ -0,0 +1,8 @@
+{
+  "scripts": {
+    "test": "jest"
+  },
+  "devDependencies": {
+    "jest": "^30.2.0"
+  }
+}

From 4c5b4703e1295785d1120d77ed6813f19e9d632e Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Tue, 11 Nov 2025 22:16:54 +0000
Subject: [PATCH 05/10] Completed lookup

---
 Sprint-2/implement/lookup.js      |  4 ++--
 Sprint-2/implement/lookup.test.js | 16 +++++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..dcbb17109 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,5 @@
-function createLookup() {
-  // implementation here
+function createLookup(arrayPairs) {
+  return Object.fromEntries(arrayPairs);
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..5974fcdfd 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,20 @@
 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", () => {
+  const arrayPairs = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const object = {
+    US: "USD",
+    CA: "CAD",
+  };
+
+  const result = createLookup(arrayPairs);
+
+  expect(result).toEqual(object);
+});
 
 /*
 

From f47f94d333905c0b2331bf3877a2c8673918743b Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Wed, 12 Nov 2025 13:35:30 +0000
Subject: [PATCH 06/10] Completed tally

---
 Sprint-2/implement/tally.js      | 10 +++++++++-
 Sprint-2/implement/tally.test.js | 21 ++++++++++++++++++++-
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..430447f2d 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,11 @@
-function tally() {}
+function tally(array) {
+  if (!Array.isArray(array)) throw new Error("array is not an array!");
+
+  return array.reduce((accumulator, currentValue) => {
+    const value = accumulator[currentValue];
+    accumulator[currentValue] = value ? value + 1 : 1;
+    return accumulator;
+  }, {});
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..733a0d669 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,16 +19,35 @@ const tally = require("./tally.js");
 // Given a function called tally
 // When passed an array of items
 // Then it should return an object containing the count for each unique item
+test("output containing the count for each unique item", () => {
+  const array = ["a", "b", "c"];
+  const result = tally(array);
+  const output = { a: 1, b: 1, c: 1 };
+  expect(result).toEqual(output);
+});
 
 // 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", () => {
+  const array = [];
+  const result = tally(array);
+  expect(result).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("array with duplicate items", () => {
+  const array = ["a", "b", "b", "c", "c", "c"];
+  const result = tally(array);
+  const output = { a: 1, b: 2, c: 3 };
+  expect(result).toEqual(output);
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("invalid input", () => {
+  expect(() => tally("Hello, World!")).toThrow("array is not an array!");
+});

From fbbf17a157b535bfc996b2a639d73157226a4948 Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Wed, 12 Nov 2025 14:15:15 +0000
Subject: [PATCH 07/10] Refactor function parseQueryString()

---
 Sprint-2/implement/querystring.js | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..e1fca45bf 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,12 +1,11 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
-  }
-  const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+  if (!queryParams) return queryParams;
+
+  const searchParameters = new URLSearchParams(queryString);
+
+  for (const [key, value] of searchParameters.entries()) {
     queryParams[key] = value;
   }
 

From 386ece3d5bf966ffba0b3fc292eb19cdd3101179 Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Wed, 12 Nov 2025 14:36:15 +0000
Subject: [PATCH 08/10] Write tests in querystring.test

---
 Sprint-2/implement/querystring.test.js | 100 +++++++++++++++++++++++--
 1 file changed, 95 insertions(+), 5 deletions(-)

diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..25e602926 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,10 +3,100 @@
 // 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 querystring values containing =", () => {
-  expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
-  });
+// Verifies that raw '+' characters are interpreted as spaces by URLSearchParams
+test("parses query string values with unencoded '+' as spaces", () => {
+  const result = parseQueryString("equation=x=y+1");
+  const output = { equation: "x=y 1" }; // because URLSearchParams decodes '+' as a space according to URL encoding rules
+  expect(result).toEqual(output);
+});
+
+// Verifies that properly URL-encoded '=' and '+' characters are preserved correctly
+test("parses query string values with encoded '=' and '+' correctly", () => {
+  const result = parseQueryString("equation=x%3Dy%2B1"); // '%3D' => '=', '%2B' => '+'
+  const output = { equation: "x=y+1" }; // because URLSearchParams decodes percent-encoded characters but preserves literal '+' when encoded as '%2B'
+  expect(result).toEqual(output);
+});
+
+test("returns empty object for empty string", () => {
+  const result = parseQueryString();
+  const output = {};
+  expect(result).toEqual(output);
+});
+
+test("handles undefined input", () => {
+  const result = parseQueryString(undefined);
+  const output = {};
+  expect(result).toEqual(output);
+});
+
+test("handles null input", () => {
+  const result = parseQueryString(null);
+  const output = {};
+  expect(result).toEqual(output);
+});
+
+test("handles key without value", () => {
+  const result = parseQueryString("name=");
+  const output = { name: "" };
+  expect(result).toEqual(output);
+});
+
+test("handles missing key", () => {
+  const result = parseQueryString("=John");
+  const output = { "": "John" };
+  expect(result).toEqual(output);
+});
+
+test("handles multiple key-value pairs", () => {
+  const result = parseQueryString("name=John&age=30&city=London");
+  const output = {
+    name: "John",
+    age: "30",
+    city: "London",
+  };
+  expect(result).toEqual(output);
+});
+
+test("handles duplicate keys by overwriting previous value", () => {
+  const result = parseQueryString("tag=js&tag=web");
+  const output = { tag: "web" };
+  expect(result).toEqual(output);
+});
+
+test("handles URL-encoded characters", () => {
+  const result = parseQueryString("city=New%20York");
+  const output = { city: "New York" };
+  expect(result).toEqual(output);
+});
+
+test("handles unencoded special characters", () => {
+  const result = parseQueryString("greeting=hello world");
+  const output = { greeting: "hello world" };
+  expect(result).toEqual(output);
+});
+
+test("handles keys containing '='", () => {
+  const result = parseQueryString("a=b=c=d");
+  const output = { a: "b=c=d" };
+  expect(result).toEqual(output);
+});
+
+test("ignores leading and trailing ampersands", () => {
+  const result = parseQueryString("&name=John&age=30&");
+  const output = { name: "John", age: "30" };
+  expect(result).toEqual(output);
+});
+
+test("ignores empty pairs", () => {
+  const result = parseQueryString("name=John&&age=30&");
+  const output = { name: "John", age: "30" };
+  expect(result).toEqual(output);
+});
+
+test("handles equals sign only", () => {
+  const result = parseQueryString("=");
+  const output = { "": "" };
+  expect(result).toEqual(output);
 });

From ea28e69a697f2e888424f2ebc015804a7b985223 Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Wed, 12 Nov 2025 16:59:16 +0000
Subject: [PATCH 09/10] Completed invert, refactored function invert() and
 created invert.test.js file to write tests.

---
 Sprint-2/interpret/invert.js      | 23 ++++++++++++++-
 Sprint-2/interpret/invert.test.js | 48 +++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 1 deletion(-)
 create mode 100644 Sprint-2/interpret/invert.test.js

diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..052560785 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -7,23 +7,44 @@
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
 function invert(obj) {
+  if (obj === null || typeof obj !== "object") {
+    throw new Error("Parameter `obj` must be an object type");
+  }
+
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+module.exports = invert;
+
 // 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 }
+
 // c) What does Object.entries return? Why is it needed in this program?
 
+// Returns an array of key/values of the enumerable own properties of an object
+// It is a convenient way to map the object properties and values into key-value pairs
+
 // d) Explain why the current return value is different from the target output
 
+// Because of this line:
+// invertedObj.key = value;
+// The property "key" is declared and the value is assigned to the "key" property
+
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+// Refer to invert.test.js
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..f35fc3138
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,48 @@
+const invert = require("./invert.js");
+
+describe("invert()", () => {
+  test("inverts an object with a single property", () => {
+    const object = { a: 1 };
+    const result = invert(object);
+    const output = { 1: "a" };
+    expect(result).toEqual(output);
+  });
+
+  test("inverts an object with multiple properties", () => {
+    const object = { a: 1, b: 2, c: 3 };
+    const result = invert(object);
+    const output = { 1: "a", 2: "b", 3: "c" };
+    expect(result).toEqual(output);
+  });
+
+  test("handles duplicate values (last key wins)", () => {
+    const object = { a: 1, b: 1, c: 2 };
+    const result = invert(object);
+    const output = { 1: "b", 2: "c" };
+    expect(result).toEqual(output);
+  });
+
+  test("handles non-string values as keys", () => {
+    const object = { a: true, b: null, c: undefined };
+    const result = invert(object);
+    const output = { true: "a", null: "b", undefined: "c" };
+    expect(result).toEqual(output);
+  });
+
+  test("handles empty object", () => {
+    const object = {};
+    const result = invert(object);
+    const output = {};
+    expect(result).toEqual(output);
+  });
+
+  test("throws error for non-object input", () => {
+    expect(() => invert(null)).toThrow(
+      "Parameter `obj` must be an object type"
+    );
+    expect(() => invert(42)).toThrow("Parameter `obj` must be an object type");
+    expect(() => invert("string")).toThrow(
+      "Parameter `obj` must be an object type"
+    );
+  });
+});

From 6ae2abb03a6477c9d49ea1f7b6c60d576976f3cc Mon Sep 17 00:00:00 2001
From: Ammad <anosidium@hotmail.com>
Date: Fri, 21 Nov 2025 17:31:42 +0000
Subject: [PATCH 10/10] Address the issues from the pull request comments

---
 Sprint-2/debug/recipe.js    | 10 +++++-----
 Sprint-2/implement/tally.js |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 0301114f0..e82edad0f 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -12,8 +12,8 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`titie: ${recipe.title}, serves: ${recipe.serves}, ingredients:\n`);
-
-for (const ingredient of recipe.ingredients) {
-  console.log(ingredient);
-}
+console.log(
+  `titie: ${recipe.title}, serves: ${
+    recipe.serves
+  }, ingredients: ${recipe.ingredients.join(", ")}`
+);
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index 430447f2d..02b621fd4 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -5,7 +5,7 @@ function tally(array) {
     const value = accumulator[currentValue];
     accumulator[currentValue] = value ? value + 1 : 1;
     return accumulator;
-  }, {});
+  }, Object.create(null));
 }
 
 module.exports = tally;