From 13acaf43082c3d044294dff35436daf43c254c7c Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Tue, 25 Nov 2025 00:22:32 +0000
Subject: [PATCH 01/26] Address.js log function corrected

---
 Sprint-2/debug/address.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..36baf9306 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+ // address is an object, so we can't access it by address[0] like in array we need to use a notation
+// address.houseNumber, address.street, address.city etc ...
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +15,9 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+
+console.log(`My house number is ${address.houseNumber}`);
+
+
+
+// Address.js log function corrected 

From 7f8b2248946fcaeb005460b04945ec419b181366 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Tue, 25 Nov 2025 00:25:50 +0000
Subject: [PATCH 02/26] Author.js corrected.

---
 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..e7187d820 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,9 @@
 // Predict and explain first...
 
+// I thought the value in the log needed to get attached with the author like value.author 
+// But the error was author is not iterable as it is an object, so we need to modify the for ... of loop as
+// for(const value of Object.values(author))
+
 // 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
 
@@ -11,6 +15,8 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
+
+// Author.js corrected.
\ No newline at end of file

From ba4ef984c49cf57d44d7aefa986dba8d5197e70a Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Tue, 25 Nov 2025 00:26:56 +0000
Subject: [PATCH 03/26] recipe.js log function corrected.

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

diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..e998ed74f 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -12,4 +12,10 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join(", ")}`);
+
+
+// I guess, because the values of ingredients are given as array, 
+// the way ingredients is passed to the log is not right.   
+
+// recipe.js log function corrected. 
\ No newline at end of file

From 6453fe492cc7eb3a600cb6e86498aee72013935f Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Tue, 25 Nov 2025 00:28:11 +0000
Subject: [PATCH 04/26] contains.js function implemented and tested.

---
 Sprint-2/implement/contains.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..2bf9a9e2a 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,11 @@
-function contains() {}
+function contains(obj, key) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+}
+return key in obj;
+
+}
 
 module.exports = contains;
+
+// In contains.js function implemented and tested. 

From cb4642b11f6493e22df3b06fe6d5cdf8ca654b2f Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Tue, 25 Nov 2025 00:29:39 +0000
Subject: [PATCH 05/26] In contains.test.js tests for contains.test.js passed

---
 Sprint-2/implement/contains.test.js | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..48c56f425 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -17,19 +17,46 @@ as the object doesn't contains a key of 'c'
 // When passed an object and a property name
 // Then it should return true if the object contains the property, false otherwise
 
+test("Should return true when key exists in object", () => {
+  const obj = { a: 1, b: 2 };
+  expect(contains(obj, "a")).toEqual(true);
+});
+
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+//test.todo("contains on empty object returns false");
+
+test("Should return false when empty object is passed", () => {
+  const obj = {};  // empty object
+  expect(contains(obj, "a")).toEqual(false);
+})
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
 
+test("Should return true when object has the property", () => {
+  const obj = { a: 5, c: 6, r: 5 };
+  expect(contains(obj, "c")).toEqual(true);
+});
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
 
+test("Should return false when object does not have the property", () => {
+  const obj = { a: 5, c: 6, r: 5 };
+  expect(contains(obj, "z")).toEqual(false); // non-existent property name
+});
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+
+test("Should return false when invalid parameters are used", () => {
+  expect(contains([], "a")).toEqual(false);      // array
+  expect(contains(null, "a")).toEqual(false);    // null 
+  expect(contains(5, "a")).toEqual(false);       // number 
+  expect(contains("hello", "a")).toEqual(false); // string 
+})
+
+// In contains.test.js tests for contains.test.js passed 
\ No newline at end of file

From 9dd1769d03dff7c644fc7a5c132823e515711db1 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 26 Nov 2025 19:32:32 +0000
Subject: [PATCH 06/26] In lookup.js function createLookup implemented.

---
 Sprint-2/implement/lookup.js | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..03176b1c8 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,27 @@
-function createLookup() {
-  // implementation here
+function createLookup(input) {
+  if (!Array.isArray(input)) {
+    throw new Error("Input must be an array of [country, currency] pairs");
+  }
+
+  const lookup = {};
+
+  for (const pair of input) {
+    if (!Array.isArray(pair) || pair.length !== 2) {
+      throw new Error("Each item must be an array of [country, currency]");
+    }
+
+    const [country, currency] = pair;
+
+    if (typeof country !== "string" || typeof currency !== "string") {
+      throw new Error("Each item must be an array of [country, currency]");
+    }
+
+    lookup[country] = currency;
+  }
+
+  return lookup;
 }
 
 module.exports = createLookup;
+
+// In lookup.js function createLookup implemented. 
\ No newline at end of file

From 8bdd6c52ea25bea9394464da8e4335a9d181fce4 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 26 Nov 2025 19:33:31 +0000
Subject: [PATCH 07/26] In lookup.test.js test cases added and passed.

---
 Sprint-2/implement/lookup.test.js | 49 ++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..a59ab3a3b 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,6 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+//test.todo("creates a country currency code lookup for multiple codes");
 
 /*
 
@@ -33,3 +33,50 @@ It should return:
    'CA': 'CAD'
  }
 */
+// Case 1: Valid input
+
+test("returns an object with country codes as keys and currency codes as values", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+  const expected = { US: "USD", CA: "CAD" };
+
+  expect(createLookup(input)).toEqual(expected);
+});
+
+// Case 2: Empty array
+
+test("returns an empty object when an empty array is passed", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+// Case 3: Input not an array
+
+test("throws an error when input is not an array", () => {
+  expect(() => createLookup("not an array")).toThrow(
+    "Input must be an array of [country, currency] pairs"
+  );
+});
+
+// Case 4: Input null or undefined
+
+test("throws an error when input is null or undefined", () => {
+  expect(() => createLookup(null)).toThrow(
+    "Input must be an array of [country, currency] pairs"
+  );
+  expect(() => createLookup(undefined)).toThrow(
+    "Input must be an array of [country, currency] pairs"
+  );
+});
+
+// Case 5: type of Input elements are not strings 
+
+  test("throws an error if inner array elements are not valid strings", () => {
+    const invalidInput = [['US', 'USD'], ['CA', 123], ['JP', null]];
+    expect(() => createLookup(invalidInput)).toThrow(
+      "Each item must be an array of [country, currency]"
+    );
+  });
+
+// In lookup.test.js test cases added and passed. 
\ No newline at end of file

From 2c0305694ff438705ec4b1d58999a9a2c218d10d Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 27 Nov 2025 11:57:15 +0000
Subject: [PATCH 08/26] In querystring.js function implemented.

---
 Sprint-2/implement/querystring.js | 43 ++++++++++++++++++++++++++-----
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..14edc8912 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,16 +1,45 @@
 function parseQueryString(queryString) {
-  const queryParams = {};
+  const parsedParams = {}; // Gets the final key-value pairs
+
+  if (!queryString) return parsedParams;
+
+  // Removes leading '?' if present
+
+  if (queryString.startsWith("?")) {
+    queryString = queryString.slice(1);
+  }
+
   if (queryString.length === 0) {
-    return queryParams;
+    return parsedParams;
   }
-  const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+  // Split the string into individual key-value pairs
+  const pairs = queryString.split("&");
+
+  for (const pair of pairs) {
+    if (!pair) continue; // skip empty segments (like from && or trailing &) eg "name=John&&age=30" 
+
+    const equalSignIndex = pair.indexOf("=");
+
+    let paramKey, paramValue;
+
+    if (equalSignIndex === -1) {
+
+      // If '=' not found we have a key exists but value is empty
+
+      paramKey = pair;
+      paramValue = "";
+    } else {
+      paramKey = decodeURIComponent(pair.slice(0, equalSignIndex));
+      paramValue = decodeURIComponent(pair.slice(equalSignIndex + 1));
+    }
+
+    parsedParams[paramKey] = paramValue; // overwrite previous value if key repeats
   }
 
-  return queryParams;
+  return parsedParams;
 }
 
 module.exports = parseQueryString;
+
+// In querystring.js function implemented. 

From 1101ce6f47d1d594a3b10e75ddda4bad7ef9ec44 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 27 Nov 2025 11:58:05 +0000
Subject: [PATCH 09/26] In querystring.test.js test edge cases added.

---
 Sprint-2/implement/querystring.test.js | 67 ++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..33ccab265 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -10,3 +10,70 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+
+// Given an empty query string
+
+test("Empty querystring returns empty object", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+// A single key with value not given
+
+test("Single Key with No Value", () => {
+  expect(parseQueryString("key=")).toEqual({ key: "" });
+});
+
+// A key without"=" sign 
+
+test("Key Without = Sign", () => {
+  expect(parseQueryString("KeyAlone")).toEqual({ KeyAlone: "" });
+});
+
+// Multiple parameters given
+
+test("Multiple Parameters", () => {
+  expect(parseQueryString("name=Smith&age=40&job=Teacher")).toEqual({
+    name: "Smith",
+    age: "40",
+    job: "Teacher",
+  });
+});
+
+// If values contain special characters
+
+test("Values Containing Special Characters", () => {
+  expect(parseQueryString("query=a%20b%26c%3Dd")).toEqual({ query: "a b&c=d" });
+});
+
+// Query starting with "?"
+
+test("Starting with ?", () => {
+  expect(parseQueryString("?foo=bar")).toEqual({ foo: "bar" });
+});
+
+// Given encoded key eg, %20  to " " 
+
+test("Encoded keys, decoded correctly", () => {
+  expect(parseQueryString("first%20name=John")).toEqual({
+    "first name": "John",
+  });
+});
+
+// Mixed encoded 
+
+test("Mixed encoded and plain parts", () => {
+  expect(parseQueryString("message=Hello%20World%21&Ans=Hello")).toEqual({
+    message: "Hello World!",
+    Ans: "Hello",
+  });
+});
+
+// Ignore  repeated symbols  --- &&
+test("Skips any empty parts that appear because of repeated symbols", () => {
+  expect(parseQueryString("a=1&&b=2")).toEqual({
+    a: "1",
+    b: "2",
+  });
+});
+
+// In querystring.test.js test edge cases added.
\ No newline at end of file

From d0665bd3f01f1e139d2911010cb4b23d12ed4e53 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 27 Nov 2025 13:28:22 +0000
Subject: [PATCH 10/26] In tally.js function tally() implemented.

---
 Sprint-2/implement/tally.js | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..0cd1ce842 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,24 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  if (items.length === 0) {
+    return {};
+  }
+
+  const counts = {};
+
+  for (const item of items) {
+
+    // Convert objects and arrays to JSON string 
+    const key = (typeof item === "object" && item !== null) ? JSON.stringify(item) : item;
+    counts[key] = (counts[key] || 0) + 1;
+  }
+
+  return counts;
+}
 
 module.exports = tally;
+
+// In tally.js function tally() implemented. 

From d471bcab93feda51bcd9df7cea0182097bd42651 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 27 Nov 2025 13:28:51 +0000
Subject: [PATCH 11/26] In tally.test.js test cases added and passed.

---
 Sprint-2/implement/tally.test.js | 81 +++++++++++++++++++++++++++++++-
 1 file changed, 80 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..fbf13122a 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -23,7 +23,7 @@ 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.todo("tally on an empty array returns an empty object");
 
 // Given an array with duplicate items
 // When passed to tally
@@ -32,3 +32,82 @@ test.todo("tally on an empty array returns an empty object");
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+
+// Case 1:  Empty array
+
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
+
+// Case 2: Array with duplicate items
+
+test("tally with duplicate items", () => {
+  expect(tally(["a", "a", "a"])).toEqual({ a: 3 });
+  expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+});
+
+// Cas 3: Array of arrays
+
+test("tally handles arrays as items", () => {
+  const input = [
+    [1, 2],
+    [1, 2],
+    [3, 4],
+  ];
+  const output = {
+    "[1,2]": 2,
+    "[3,4]": 1,
+  };
+  expect(tally(input)).toEqual(output);
+});
+
+// case 4: Array of objects
+
+test("tally handles objects as items", () => {
+  const input = [{ a: 1 }, { a: 1 }, { b: 2 }];
+  const output = {
+    '{"a":1}': 2,
+    '{"b":2}': 1,
+  };
+  expect(tally(input)).toEqual(output);
+});
+
+// Case 5: Mixed array of arrays and objects
+
+test("tally handles mixed arrays and objects", () => {
+  const input = [[1, 2], { a: 1 }, [1, 2], { a: 1 }, { b: 2 }];
+  const output = {
+    "[1,2]": 2,
+    '{"a":1}': 2,
+    '{"b":2}': 1,
+  };
+  expect(tally(input)).toEqual(output);
+});
+
+// Case 6:  Mixed types (numbers, strings, booleans)
+
+test("tally handles numbers, strings, and booleans", () => {
+  const input = [1, "1", true, true, false];
+  const output = { 1: 2, true: 2, false: 1 };
+  expect(tally(input)).toEqual(output);
+});
+
+// Case 7: Array with null and undefined
+
+test("tally handles null and undefined values", () => {
+  const input = [null, null, undefined];
+  const output = { null: 2, undefined: 1 };
+  expect(tally(input)).toEqual(output);
+});
+
+// Case 8: Invalid input: non-array
+
+test("tally throws error if input is not an array", () => {
+  expect(() => tally("not an array")).toThrow("Input must be an array");
+  expect(() => tally(123)).toThrow("Input must be an array");
+  expect(() => tally({ a: 1 })).toThrow("Input must be an array");
+  expect(() => tally(null)).toThrow("Input must be an array");
+  expect(() => tally(undefined)).toThrow("Input must be an array");
+});
+
+// In tally.test.js test cases added and passed.

From e550d17e9f0ccde52b8c978b127981d68338901b Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 4 Dec 2025 19:09:01 +0000
Subject: [PATCH 12/26] In invert.js invert function implemented.

---
 Sprint-2/interpret/invert.js | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..2c31d5cff 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -7,23 +7,46 @@
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
 function invert(obj) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    throw new Error("Input must be an object");
+  }
+
   const invertedObj = {};
 
-  for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+  for (let [key, value] of Object.entries(obj)) {
+    if (typeof key === "object") {
+      key = JSON.stringify(key);
+    }
+    if (typeof value === "object") {
+      value = JSON.stringify(value);
+    }
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+module.exports = invert;
 // a) What is the current return value when invert is called with { a : 1 }
 
+// --> current return value i {key: 1}
+
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// --> current return value i {key: 2}
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// --> Target return value is {"1": "a", "2": "b" }
 
 // c) What does Object.entries return? Why is it needed in this program?
+// --> Object.entries returns an array of key and value ['key', 'value'] pairs
+  // Given { a: 1, b: 2 } returns [['a', '1'],['b', '2']]
 
 // d) Explain why the current return value is different from the target output
+// --> invertedObj.key = value  is creating a property named key. As the loop
+    //goes through the object each value gets overwritten and we get the last 
+    // argument as a value. 
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+
+// In invert.js invert function implemented. 
\ No newline at end of file

From 218caa693d4bf5ada46e16b3ecab9bda1a04e869 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 4 Dec 2025 19:09:34 +0000
Subject: [PATCH 13/26] // In invert.test.js test cases tested.

---
 Sprint-2/interpret/invert.test.js | 45 +++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 Sprint-2/interpret/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..449adf966
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,45 @@
+const invert = require("./invert.js");
+
+// Case 1: Normal object inversion
+test("invert single-level object", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ "1": "a", "2": "b" });
+});
+
+// Case 2: object with string values
+test("invert object with string values", () => {
+  expect(invert({ x: "CYF", y: "abc" })).toEqual({ "CYF": "x", "abc": "y" });
+});
+
+// Case 3: object with boolean values
+test("invert object with boolean values", () => {
+  expect(invert({ a: true, b: false })).toEqual({ "true": "a", "false": "b" });
+});
+
+// Case 4: object with nested object as value
+test("invert object with nested object as value", () => {
+  const input = { a: { x: 1 }, b: 2 };
+  const expected = { '{"x":1}': "a", "2": "b" };
+  expect(invert(input)).toEqual(expected);
+});
+
+// Case 5: object with duplicate values 
+test("invert object with duplicate values", () => {
+  const input = { a: 1, b: 1 };
+  const expected = { "1": "b" };
+  expect(invert(input)).toEqual(expected);
+});
+
+// Case 6: empty object
+test("invert empty object", () => {
+  expect(invert({})).toEqual({});
+});
+
+// Case 7: invalid inputs (non-object)
+test("throws error for non-object input", () => {
+  expect(() => invert(null)).toThrow("Input must be an object");
+  expect(() => invert(42)).toThrow("Input must be an object");
+  expect(() => invert("foo")).toThrow("Input must be an object");
+  expect(() => invert([1,2,3])).toThrow("Input must be an object");
+});
+
+// In invert.test.js test cases tested.
\ No newline at end of file

From d2985e477596d45d40992969b0c90388bd5a0a52 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 4 Dec 2025 20:00:57 +0000
Subject: [PATCH 14/26] In count-words.js function countWords implemented.

---
 Sprint-2/stretch/count-words.js | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Sprint-2/stretch/count-words.js b/Sprint-2/stretch/count-words.js
index 8e85d19d7..e6bcc235e 100644
--- a/Sprint-2/stretch/count-words.js
+++ b/Sprint-2/stretch/count-words.js
@@ -25,4 +25,32 @@
 2. Ignore the case of the words to find more unique words. e.g. (A === a, Hello === hello)
 
 3. Order the results to find out which word is the most common in the input
+
 */
+function countWords(string) {
+  //  validation of input
+  if (typeof string !== "string") {
+    throw new Error("Input should be a string");
+  }
+  if (string === "") return {};
+  const counts = {};
+
+  // Remove punctuation and lowercase everything
+  
+  const cleanText = string.replace(/[.,!?]/g, "").toLowerCase();
+  const words = cleanText.split(" ");
+
+  // Count word frequencies
+  for (const word of words) {
+    counts[word] = (counts[word] || 0) + 1;
+  }
+
+  // Sort by frequency (most common first)
+  const sorted = Object.entries(counts).sort((a, b) => b[1] - a[1]);
+
+  return Object.fromEntries(sorted);
+}
+
+console.log(countWords("Hello!, my friend, You and me, and you."));
+
+// In count-words.js function countWords implemented. 

From 6dff1386e70235e265125d2f7c67669930f558dd Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 4 Dec 2025 20:01:52 +0000
Subject: [PATCH 15/26] In mode.js function calculateMode refactored.

---
 Sprint-2/stretch/mode.js | 62 +++++++++++++++++++++++++++++++++-------
 1 file changed, 51 insertions(+), 11 deletions(-)

diff --git a/Sprint-2/stretch/mode.js b/Sprint-2/stretch/mode.js
index 3f7609d79..13e72112b 100644
--- a/Sprint-2/stretch/mode.js
+++ b/Sprint-2/stretch/mode.js
@@ -8,29 +8,69 @@
 // refactor calculateMode by splitting up the code
 // into smaller functions using the stages above
 
-function calculateMode(list) {
-  // track frequency of each value
-  let freqs = new Map();
+// function calculateMode(list) {
+//   // track frequency of each value
+//   let freqs = new Map();
 
-  for (let num of list) {
-    if (typeof num !== "number") {
-      continue;
-    }
+//   for (let num of list) {
+//     if (typeof num !== "number") {
+//       continue;
+//     }
+
+//     freqs.set(num, (freqs.get(num) || 0) + 1);
+//   }
+
+//   // Find the value with the highest frequency
+//   let maxFreq = 0;
+//   let mode;
+//   for (let [num, freq] of freqs) {
+//     if (freq > maxFreq) {
+//       mode = num;
+//       maxFreq = freq;
+//     }
+//   }
+
+//   return maxFreq === 0 ? NaN : mode;
+//}
+
+
+// -------------- refactored  ------------- //
+
+// Phase 1: Count the frequency of each number
+
+function countFrequency(list) {
+  const frequency = new Map();
 
-    freqs.set(num, (freqs.get(num) || 0) + 1);
+  for (const num of list) {
+    if (typeof num !== "number") continue; // skip non-numbers
+    frequency.set(num, (frequency.get(num) || 0) + 1);
   }
 
-  // Find the value with the highest frequency
+  return frequency;
+}
+
+// Stage 2: Find the number with the highest frequency
+function findMode(frequency) {
   let maxFreq = 0;
   let mode;
-  for (let [num, freq] of freqs) {
+
+  for (const [num, freq] of frequency) {
     if (freq > maxFreq) {
-      mode = num;
       maxFreq = freq;
+      mode = num;
     }
   }
 
   return maxFreq === 0 ? NaN : mode;
 }
 
+// Main function
+function calculateMode(list) {
+  const frequency = countFrequency(list);
+  return findMode(frequency);
+}
+console.log(calculateMode([1, 2, 2, 3, 3, 3, 4]));
+
 module.exports = calculateMode;
+
+// In mode.js function calculateMode refactored. 

From 0088e751e9d5ef949eeb1ab19c7515ed920b8c3f Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Thu, 4 Dec 2025 20:09:37 +0000
Subject: [PATCH 16/26] In mode.test.js test cases passed

---
 Sprint-2/stretch/mode.test.js | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/Sprint-2/stretch/mode.test.js b/Sprint-2/stretch/mode.test.js
index ca33c28a3..241ebe8de 100644
--- a/Sprint-2/stretch/mode.test.js
+++ b/Sprint-2/stretch/mode.test.js
@@ -13,20 +13,29 @@ const calculateMode = require("./mode.js");
 
 describe("calculateMode()", () => {
   test("returns the most frequent number in an array", () => {
-    const nums = [2, 4, 1, 2, 3, 2, 1];
+    const arr = [2, 4, 1, 2, 3, 2, 1];
 
-    expect(calculateMode(nums)).toEqual(2);
+    expect(calculateMode(arr)).toEqual(2);
   });
 
   test("returns the first mode in case of multiple modes", () => {
-    const nums = [1, 2, 2, 3, 3];
+    const arr = [1, 2, 2, 3, 3];
 
-    expect(calculateMode(nums)).toEqual(2);
+    expect(calculateMode(arr)).toEqual(2);
   });
 
   test("ignores non-number values", () => {
-    const nums = [1, 3, "2", 2, 3, null];
+    const arr = [1, 3, "2", 2, 3, null];
 
-    expect(calculateMode(nums)).toEqual(3);
+    expect(calculateMode(arr)).toEqual(3);
   });
+
+  test("returns NaN for an empty array", () => {
+  expect(calculateMode([])).toEqual();
+});
+
 });
+
+// In mode.test.js test cases passed
+
+

From bd20fa115b6d3fb94d35542ff1362f86b6cebc94 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Sat, 6 Dec 2025 14:16:32 +0000
Subject: [PATCH 17/26] In till.js function implemented.

---
 Sprint-2/stretch/till.js | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/Sprint-2/stretch/till.js b/Sprint-2/stretch/till.js
index 6a08532e7..f95a5bd14 100644
--- a/Sprint-2/stretch/till.js
+++ b/Sprint-2/stretch/till.js
@@ -5,27 +5,35 @@
 // Then it should return the total amount in pounds
 
 function totalTill(till) {
+  if (typeof till !== "object" || till === null || Array.isArray(till)) {
+    throw new Error("Input should be an object");
+  }
+
   let total = 0;
 
   for (const [coin, quantity] of Object.entries(till)) {
-    total += coin * quantity;
+    const value = parseInt(coin); // extracts the numeric part
+
+    if (isNaN(value)) continue;
+
+    total += value * quantity;
   }
 
-  return `£${total / 100}`;
+  const pounds = Math.floor(total / 100);
+  const pence = String(total % 100).padStart(2, "0");
+
+  return `£${pounds}.${pence}`;
 }
 
-const till = {
-  "1p": 10,
-  "5p": 6,
-  "50p": 4,
-  "20p": 10,
-};
-const totalAmount = totalTill(till);
+module.exports = totalTill;
 
 // a) What is the target output when totalTill is called with the till object
-
+// --> The target output should be £4.40
 // b) Why do we need to use Object.entries inside the for...of loop in this function?
-
+// --> To get both the key and value of the till object inside the loop.
 // c) What does coin * quantity evaluate to inside the for...of loop?
-
+// --> It is supposed to calculate the total number of pence
 // d) Write a test for this function to check it works and then fix the implementation of totalTill
+
+
+// In till.js function implemented. 
\ No newline at end of file

From 3735e91b9c9e5cb64f63fc889620d4db28b070d3 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Sat, 6 Dec 2025 14:17:01 +0000
Subject: [PATCH 18/26] In till.test.js test cases written and tested.

---
 Sprint-2/stretch/till.test.js | 49 +++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 Sprint-2/stretch/till.test.js

diff --git a/Sprint-2/stretch/till.test.js b/Sprint-2/stretch/till.test.js
new file mode 100644
index 000000000..08abbe8d7
--- /dev/null
+++ b/Sprint-2/stretch/till.test.js
@@ -0,0 +1,49 @@
+const totalTill = require("./till.js");
+
+describe("totalTill()", () => {
+  test("correctly totals a simple till", () => {
+    const till = {
+      "1p": 10,    // 10p
+      "5p": 6,     // 30p
+      "20p": 10,   // 200p
+      "50p": 4,    // 200p
+    };
+   
+    expect(totalTill(till)).toBe("£4.40");
+  });
+
+  test("ignores invalid coin types", () => {
+    const till = {
+      "1p": 2,     // 2p
+      "abc": 10,  // ignore
+      "£1": 5,     
+    };
+
+    expect(totalTill(till)).toEqual("£0.02");
+  });
+
+  test("handles empty till", () => {
+    expect(totalTill({})).toEqual("£0.00");
+  });
+
+  test("throws an error for non-object input", () => {
+    expect(() => totalTill(null)).toThrow("Input should be an object");
+    expect(() => totalTill(5)).toThrow("Input should be an object");
+    expect(() => totalTill("hello")).toThrow("Input should be an object");
+    expect(() => totalTill([])).toThrow("Input should be an object");
+  });
+
+  test("correct formatting for values under 10p", () => {
+    const till = { "1p": 3 }; // 3p
+    expect(totalTill(till)).toEqual("£0.03");
+  });
+
+  test("correct formatting when total is exactly whole pounds", () => {
+    const till = { "50p": 4, "20p": 5 }; 
+    // 50p*4 = 200p, 20p*5 = 100p → total = 300p = £3.00
+
+    expect(totalTill(till)).toEqual("£3.00");
+  });
+});
+
+// In till.test.js test cases written and tested. 
\ No newline at end of file

From 2f7f0e2f4402fc678c26aa615e0387b24dba938e Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 11:56:16 +0000
Subject: [PATCH 19/26] recipe.js modified  "${recipe.ingredients.join("\n")}`)
 to make ingredients appear on new line.

---
 Sprint-2/debug/recipe.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index e998ed74f..1940376c4 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -12,10 +12,11 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe.ingredients.join(", ")}`);
+${recipe.ingredients.join("\n")}`);
 
 
 // I guess, because the values of ingredients are given as array, 
 // the way ingredients is passed to the log is not right.   
 
-// recipe.js log function corrected. 
\ No newline at end of file
+// recipe.js log function corrected. 
+// recipe.js modified  "${recipe.ingredients.join("\n")}`) to make ingredients appear on new line.
\ No newline at end of file

From 161b8710a9ef72210f47c266276748bf585f9f13 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 12:42:24 +0000
Subject: [PATCH 20/26] In contains.js modified return function as return
 Object.hasOwn(obj, key);

---
 Sprint-2/implement/contains.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index 2bf9a9e2a..8c8b8f98d 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -2,10 +2,17 @@ function contains(obj, key) {
   if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
     return false;
 }
-return key in obj;
+//return key in obj;
+return Object.hasOwn(obj, key);
 
 }
 
 module.exports = contains;
 
 // In contains.js function implemented and tested. 
+
+  let obj = {}, propertyName = "toString";
+  console.log( propertyName in obj );                // true
+  console.log( Object.hasOwn(obj, propertyName) );   // false
+
+  // In contains.js modified return function as return Object.hasOwn(obj, key);
\ No newline at end of file

From 5cddc238ba9bc24a9e9bdfeff1150d7e4dc0321f Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 13:01:44 +0000
Subject: [PATCH 21/26] contains.test.js re-tested.

---
 Sprint-2/implement/contains.test.js | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 48c56f425..9e8743d8c 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -53,10 +53,14 @@ test("Should return false when object does not have the property", () => {
 // Then it should return false or throw an error
 
 test("Should return false when invalid parameters are used", () => {
-  expect(contains([], "a")).toEqual(false);      // array
+  expect(contains([1, 2, 3], "1")).toEqual(true); // "1" is a key
+  expect(contains([1, 2, 3], "3")).toEqual(false); // "3" is not a key
+  //expect(contains([], "a")).toEqual(false);      // array
   expect(contains(null, "a")).toEqual(false);    // null 
   expect(contains(5, "a")).toEqual(false);       // number 
   expect(contains("hello", "a")).toEqual(false); // string 
 })
 
-// In contains.test.js tests for contains.test.js passed 
\ No newline at end of file
+// In contains.test.js tests for contains.test.js passed 
+
+// contains.test.js re-tested.
\ No newline at end of file

From aab642f09e10b79779398e0d2bef77fc4cb602a9 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 15:19:24 +0000
Subject: [PATCH 22/26] Decoding of   paramKey = decodeURIComponent(pair);
 added.

---
 Sprint-2/implement/querystring.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 14edc8912..de4a8eb70 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -27,7 +27,7 @@ function parseQueryString(queryString) {
 
       // If '=' not found we have a key exists but value is empty
 
-      paramKey = pair;
+      paramKey = decodeURIComponent(pair);
       paramValue = "";
     } else {
       paramKey = decodeURIComponent(pair.slice(0, equalSignIndex));
@@ -43,3 +43,4 @@ function parseQueryString(queryString) {
 module.exports = parseQueryString;
 
 // In querystring.js function implemented. 
+// Decoding of   paramKey = decodeURIComponent(pair); added. 
\ No newline at end of file

From 7ef1f9c60891b8373cc1140e0e676d02f835ecd6 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 15:42:20 +0000
Subject: [PATCH 23/26] In tally.js  modification made.

---
 Sprint-2/implement/tally.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index 0cd1ce842..cad5ee856 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -7,7 +7,7 @@ function tally(items) {
     return {};
   }
 
-  const counts = {};
+  const counts = Object.create(null);
 
   for (const item of items) {
 
@@ -19,6 +19,11 @@ function tally(items) {
   return counts;
 }
 
+console.log(tally(["toStrin", "toStrin"]));
+console.log(tally(["toString", "toString"]));
+
 module.exports = tally;
 
 // In tally.js function tally() implemented. 
+
+// modification made. 

From ba1bc62c5b825f27578348d162bf976d9e9df6e4 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 15:45:47 +0000
Subject: [PATCH 24/26] Modified to handle inherent property cases and to
 remove empty spaces.

---
 Sprint-2/stretch/count-words.js | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Sprint-2/stretch/count-words.js b/Sprint-2/stretch/count-words.js
index e6bcc235e..7ed1433d9 100644
--- a/Sprint-2/stretch/count-words.js
+++ b/Sprint-2/stretch/count-words.js
@@ -33,12 +33,12 @@ function countWords(string) {
     throw new Error("Input should be a string");
   }
   if (string === "") return {};
-  const counts = {};
+  const counts = Object.create(null) // prevents inherent properties.
 
   // Remove punctuation and lowercase everything
   
   const cleanText = string.replace(/[.,!?]/g, "").toLowerCase();
-  const words = cleanText.split(" ");
+  const words = cleanText.split(" ").filter(Boolean); // removes empty strings
 
   // Count word frequencies
   for (const word of words) {
@@ -52,5 +52,9 @@ function countWords(string) {
 }
 
 console.log(countWords("Hello!, my friend, You and me, and you."));
+console.log(countWords("constructor constructor"));
+console.log(countWords("          Hello   World      "));
 
 // In count-words.js function countWords implemented. 
+
+// Modified to handle inherent property cases and to remove empty spaces. 

From 2528d55cb57f0a619cacfb485f9b072b2d906bb6 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 16:59:00 +0000
Subject: [PATCH 25/26] The  "if (typeof obj !== "object" || obj === null)"
 modified.

---
 Sprint-2/implement/contains.js | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index 8c8b8f98d..f3c8c0c33 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,7 +1,7 @@
 function contains(obj, key) {
-  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+  if (typeof obj !== "object" || obj === null) {
     return false;
-}
+  }
 //return key in obj;
 return Object.hasOwn(obj, key);
 
@@ -15,4 +15,5 @@ module.exports = contains;
   console.log( propertyName in obj );                // true
   console.log( Object.hasOwn(obj, propertyName) );   // false
 
-  // In contains.js modified return function as return Object.hasOwn(obj, key);
\ No newline at end of file
+  // In contains.js modified return function as return Object.hasOwn(obj, key);
+  // The  "if (typeof obj !== "object" || obj === null)" modified.
\ No newline at end of file

From 8e4807e51132b7742bad2dbea0229e77c918f665 Mon Sep 17 00:00:00 2001
From: UbunMen <mahtem23@gmail.com>
Date: Wed, 10 Dec 2025 17:29:54 +0000
Subject: [PATCH 26/26] Test case description updated

---
 Sprint-2/implement/contains.test.js | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 9e8743d8c..5bd2c50e2 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -52,15 +52,19 @@ test("Should return false when object does not have the property", () => {
 // When passed to contains
 // Then it should return false or throw an error
 
-test("Should return false when invalid parameters are used", () => {
+test("Should correctly detect keys in arrays", () => {
   expect(contains([1, 2, 3], "1")).toEqual(true); // "1" is a key
   expect(contains([1, 2, 3], "3")).toEqual(false); // "3" is not a key
-  //expect(contains([], "a")).toEqual(false);      // array
-  expect(contains(null, "a")).toEqual(false);    // null 
+});
+
+test("Should return false when invalid parameters are used", () => {
+   expect(contains(null, "a")).toEqual(false);    // null 
   expect(contains(5, "a")).toEqual(false);       // number 
   expect(contains("hello", "a")).toEqual(false); // string 
 })
 
 // In contains.test.js tests for contains.test.js passed 
 
-// contains.test.js re-tested.
\ No newline at end of file
+// contains.test.js re-tested.
+
+// test case description differentiated. 
\ No newline at end of file