From 15a213d2f6bae351483f326674980711d9083a72 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Thu, 12 Mar 2026 18:08:04 +0000
Subject: [PATCH 01/11] files have been debugged in debug folder of sprint-2

---
 Sprint-2/debug/address.js | 2 +-
 Sprint-2/debug/author.js  | 7 +++++--
 Sprint-2/debug/recipe.js  | 8 ++++++--
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..36d2f865d 100644
--- a/Sprint-2/debug/address.js
+++ b/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}`);
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..4612b723d 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -3,6 +3,9 @@
 // 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
 
+// ==> this code is looping through an object and only return the key not the value.
+// ==> After testing I found that (for of) does not loop directly in objects and it was throwing error "author is not iterable". In this case we should use (for in) to iterate.
+
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +14,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const value in author) {
+  console.log(author[value]);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..abb87ece7 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,8 +1,10 @@
 // Predict and explain first...
+// ==> this code is not correct as the ingredients act as string not an object key therefore we wont have the value.
 
 // 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?
+// ==> to fix the issue and print each ingredients in new line we need to loop through the array inside our recipe object.
 
 const recipe = {
   title: "bruschetta",
@@ -11,5 +13,7 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:`);
+for (let fruits of recipe.ingredients) {
+  console.log(fruits);
+}

From ad212d7c7d4bd90e190f73b9c74378eee3522f95 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Mon, 16 Mar 2026 11:21:18 +0000
Subject: [PATCH 02/11] Jest test added and Functions were fixed

---
 Sprint-2/implement/contains.js         | 17 ++++++++++++-
 Sprint-2/implement/contains.test.js    | 34 ++++++++++++++++++++++++--
 Sprint-2/implement/lookup.js           | 16 +++++++++---
 Sprint-2/implement/lookup.test.js      | 18 +++++++++++---
 Sprint-2/implement/querystring.js      | 20 ++++++++++-----
 Sprint-2/implement/querystring.test.js |  4 +--
 Sprint-2/implement/tally.js            | 16 ++++++++++--
 Sprint-2/implement/tally.test.js       | 18 ++++++++++++--
 8 files changed, 122 insertions(+), 21 deletions(-)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..b509ba799 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,18 @@
-function contains() {}
+// start your function
+
+function contains(object, key) {
+  if (Array.isArray(object) && Object.keys(object).length === 0) {
+    return false;
+  } else if (object.hasOwnProperty(key)) {
+    return true;
+  } else return false;
+}
+
+let key = "name";
+const object = {
+  name: "Roman",
+  age: 33,
+  city: "Birmingham",
+};
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..2713519ca 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -15,21 +15,51 @@ 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
+// Then it should return true if the object contains the property,
+test("It return true when the object contains the property", () => {
+  let object = { name: "Roman", age: 34 };
+  let key = "name";
+  expect(contains(object, key)).toEqual(true);
+});
+// object does not contain the property
+test("It return false when the object does not contains the property", () => {
+  let object = { name: "Roman", age: 34 };
+  let key = "lastName";
+  expect(contains(object, key)).toEqual(false);
+});
 
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("It return false when the object has not any property", () => {
+  let object = {};
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("It returns true when the object has the specified property", () => {
+  const object = { name: "Roman", age: 34, city: "Birmingham" };
+  const key = "name";
+  expect(contains(object, key)).toEqual(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("It returns false when the object does NOT have the specified property", () => {
+  const object = { name: "Roman", age: 34, city: "Birmingham" };
+  const key = "lastName";
+  expect(contains(object, key)).toEqual(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("It return false when an array is passed instead of object", () => {
+  let object = [1, 2, 3];
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..0a01c5652 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,15 @@
-function createLookup() {
-  // implementation here
+// start your function;
+function createLookup(input) {
+  let output = {};
+  for (let pair of input) {
+    let key = pair[0];
+    let value = pair[1];
+    output[key] = value;
+  }
+  return output;
 }
-
+let input = [
+  ["US", "USD"],
+  ["CA", "CAD"],
+];
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..9d4be7c87 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,9 +1,7 @@
 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:
@@ -33,3 +31,17 @@ It should return:
    'CA': 'CAD'
  }
 */
+
+test("creates a country currency code lookup for multiple codes", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const expected = {
+    US: "USD",
+    CA: "CAD",
+  };
+
+  expect(createLookup(input)).toEqual(expected);
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..75c95c83b 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,16 +1,24 @@
+// start your function;
 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("=");
-    queryParams[key] = value;
+  // URLSearchParams is a built-in JavaScript object that can read query strings.
+  const params = new URLSearchParams(queryString); // params stores the query string internally as key-value pairs.
+  for (let pair of params) {
+    let key = pair[0];
+    let value = pair[1];
+    queryParams[key] = value.replace(/ /g, "+");
   }
-
   return queryParams;
 }
+let queryString = "equation=x=y+1";
 
 module.exports = parseQueryString;
+
+// Notice: ===>  URLSearchParams is a class, not a plain function.
+// Classes in JS must be called with new.
+// new URLSearchParams(...) → creates a new instance (object) of the class.
+// That instance knows how to store and iterate key-value pairs.
+// URLSearchParams decodes URL-encoded characters, and in query strings, a + represents a space. and this is why we need .replace(/ /g, "+");
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..717ee6901 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,10 +3,10 @@
 // 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",
+    equation: "x=y+1",
   });
 });
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..6cddd4258 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,15 @@
-function tally() {}
-
+function tally(arr) {
+  let output = {};
+  if (!Array.isArray(arr)) {
+    throw new Error("Invalid input");
+  } else if (arr.length === 0) {
+    return output;
+  }
+  for (let item of arr) {
+    let count = arr.filter((x) => x === item).length;
+    output[item] = count;
+  }
+  return output;
+}
+let arr = ["a", "b"];
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..9a0776f30 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,16 +19,30 @@ 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("returns count 1 for a single item", () => {
+  const arr = ["a"];
+  expect(tally(arr)).toEqual({ a: 1 });
+});
 
 // 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("returns an empty object when given an empty array", () => {
+  const arr = [];
+  expect(tally(arr)).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
-
+test("returns counts for each unique item for given duplicate items ", () => {
+  const arr = ["a", "a", "b", "c"];
+  expect(tally(arr)).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("it throw an error if given a string", () => {
+  const str = "a";
+  expect(() => tally(str)).toThrowError();
+});

From ef27922808b309dbbf504b9de2c6c20e518f2627 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Mon, 16 Mar 2026 14:07:31 +0000
Subject: [PATCH 03/11] inverted function and jest test implemented

---
 Sprint-2/interpret/invert.js      | 11 +++++++++--
 Sprint-2/interpret/invert.test.js | 13 +++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)
 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..3765bdbcd 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,27 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
-
+obj = { a: 1, b: 2 };
+module.exports = invert;
 // a) What is the current return value when invert is called with { a : 1 }
+// answer ===> the output will be {"key": 1}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// answer ===> the output ll be {"key": 2}
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// answer ===> the output ll be {"1": "a", "2": "b"};
 
 // c) What does Object.entries return? Why is it needed in this program?
+// answer ===> converts an object into an array of key-value pairs, we need it to loop through and access the elements.
 
 // d) Explain why the current return value is different from the target output
+// answer ===>  because of this line --> invertedObj.key = value; as it creates a "key" and assign the value to it. and with variables we need to use bracket notation not dot notation.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+// I have fixed the implementation: from invertedObj.key = value to invertedObj[value] = key;
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..4921a429b
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,13 @@
+const invert = require("./invert.js");
+// testing time
+test("Empty object returns empty object", () => {
+  expect(invert({})).toEqual({});
+});
+
+test("Single key-value pair", () => {
+  expect(invert({ a: 1 })).toEqual({ 1: "a" });
+});
+
+test("Given an object, then it should swap the keys and values in the object", () => {
+  expect(invert({ x: 10, y: 20 })).toEqual({ 10: "x", 20: "y" });
+});

From df349cf71be0384bb08f3df8289cf863a444927a Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Mon, 16 Mar 2026 17:48:13 +0000
Subject: [PATCH 04/11] test and functions implemented for stretch files

---
 Sprint-2/stretch/count-words.js | 15 +++++++++++++++
 Sprint-2/stretch/mode.js        | 31 ++++++++++++++++---------------
 Sprint-2/stretch/till.js        | 11 +++++++----
 Sprint-2/stretch/till.test.js   | 23 +++++++++++++++++++++++
 4 files changed, 61 insertions(+), 19 deletions(-)
 create mode 100644 Sprint-2/stretch/till.test.js

diff --git a/Sprint-2/stretch/count-words.js b/Sprint-2/stretch/count-words.js
index 8e85d19d7..78bd31ebf 100644
--- a/Sprint-2/stretch/count-words.js
+++ b/Sprint-2/stretch/count-words.js
@@ -12,6 +12,8 @@
 
   countWords("you and me and you") then the target output is { you: 2, and: 2, me: 1 }
 
+  
+
   To complete this exercise you should understand
     - Strings and string manipulation
     - Loops
@@ -26,3 +28,16 @@
 
 3. Order the results to find out which word is the most common in the input
 */
+function countWords(str) {
+  let cleanStr = str.split(" ");
+  let objWords = {};
+  for (let word of cleanStr) {
+    if (word !== "") continue;
+    if (objWords[word]) {
+      objWords[word]++;
+    } else {
+      objWords[word] = 1;
+    }
+  }
+  return objWords;
+}
diff --git a/Sprint-2/stretch/mode.js b/Sprint-2/stretch/mode.js
index 3f7609d79..208b3f038 100644
--- a/Sprint-2/stretch/mode.js
+++ b/Sprint-2/stretch/mode.js
@@ -9,28 +9,29 @@
 // into smaller functions using the stages above
 
 function calculateMode(list) {
-  // track frequency of each value
-  let freqs = new Map();
-
+  // Stage 1: Count frequencies
+  let freqs = {};
   for (let num of list) {
-    if (typeof num !== "number") {
-      continue;
-    }
+    if (typeof num !== "number") continue; // skip non-number values
 
-    freqs.set(num, (freqs.get(num) || 0) + 1);
+    if (freqs[num] === undefined) {
+      freqs[num] = 1;
+    } else {
+      freqs[num] += 1;
+    }
   }
-
-  // Find the value with the highest frequency
+  // Stage 2: 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;
+  let mode = null;
+
+  for (let num in freqs) {
+    if (freqs[num] > maxFreq) {
+      maxFreq = freqs[num];
+      mode = Number(num); // convert string key to number
     }
   }
 
-  return maxFreq === 0 ? NaN : mode;
+  return mode;
 }
 
 module.exports = calculateMode;
diff --git a/Sprint-2/stretch/till.js b/Sprint-2/stretch/till.js
index 6a08532e7..f61b806c3 100644
--- a/Sprint-2/stretch/till.js
+++ b/Sprint-2/stretch/till.js
@@ -8,24 +8,27 @@ function totalTill(till) {
   let total = 0;
 
   for (const [coin, quantity] of Object.entries(till)) {
-    total += coin * quantity;
+    const coinValue = parseInt(coin); // "50p" -> 50
+    total += coinValue * quantity;
   }
 
-  return `£${total / 100}`;
+  return `£${(total / 100).toFixed(2)}`;
 }
-
 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
+// ===> target output ll be 4.40 pound.
 
 // b) Why do we need to use Object.entries inside the for...of loop in this function?
+// answer ===> we need Object.entries inside the loop, as our input is a key-value pair object. to access them its the easiest way to convert them to key-value array and do the other operations.
 
 // c) What does coin * quantity evaluate to inside the for...of loop?
+// answer ===> it operates multiplication on the key and the value.
 
 // d) Write a test for this function to check it works and then fix the implementation of totalTill
diff --git a/Sprint-2/stretch/till.test.js b/Sprint-2/stretch/till.test.js
new file mode 100644
index 000000000..4751cfd92
--- /dev/null
+++ b/Sprint-2/stretch/till.test.js
@@ -0,0 +1,23 @@
+const totalTill = require("./till.js");
+
+// writing tests:
+
+test("calculates total correctly for a standard till", () => {
+  const till = { "1p": 10, "5p": 6, "50p": 4, "20p": 10 };
+  expect(totalTill(till)).toBe("£4.40");
+});
+
+test("returns £0.00 when all coins are 0", () => {
+  const till = { "1p": 0, "2p": 0, "50p": 0 };
+  expect(totalTill(till)).toBe("£0.00");
+});
+
+test("calculates correctly with only a few coins", () => {
+  const till = { "1p": 100, "50p": 2 };
+  expect(totalTill(till)).toBe("£2.00");
+});
+
+test("works with a mix of coins", () => {
+  const till = { "5p": 4, "10p": 5, "20p": 2 };
+  expect(totalTill(till)).toBe("£1.10"); // correct calculation
+});

From 4b5aff7026be5f1b20a1e961af750d0c45c1d355 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Mon, 16 Mar 2026 17:49:59 +0000
Subject: [PATCH 05/11] Nothing special

---
 Sprint-2/package-lock.json | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Sprint-2/package-lock.json b/Sprint-2/package-lock.json
index 9b4c725d6..ceda7296e 100644
--- a/Sprint-2/package-lock.json
+++ b/Sprint-2/package-lock.json
@@ -56,6 +56,7 @@
       "integrity": "sha512-Oixnb+DzmRT30qu9d3tJSQkxuygWm32DFykT4bRoORPa9hZ/L4KhVB/XiRm6KG+roIEM7DBQlmg27kw2HZkdZg==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@ampproject/remapping": "^2.2.0",
         "@babel/code-frame": "^7.25.7",
@@ -1368,6 +1369,7 @@
         }
       ],
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "caniuse-lite": "^1.0.30001663",
         "electron-to-chromium": "^1.5.28",

From 748465baace8c4a63f15b2c82b36981fa8065048 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Sun, 22 Mar 2026 18:48:15 +0000
Subject: [PATCH 06/11] recipe.js has been refactored

---
 Sprint-2/debug/recipe.js | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index abb87ece7..ef823d17f 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -13,7 +13,5 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-ingredients:`);
-for (let fruits of recipe.ingredients) {
-  console.log(fruits);
-}
+ingredients: ${recipe.ingredients.join("\n")}`);
+// this approach looks clean and advanced

From 40215f88a9202992fdc29b5807436f44f639d24e Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Sun, 22 Mar 2026 19:18:14 +0000
Subject: [PATCH 07/11] Jest tests and contains function updated

---
 Sprint-2/implement/contains.js      | 10 +++++----
 Sprint-2/implement/contains.test.js | 32 +++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index b509ba799..d0458e69e 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,11 +1,13 @@
 // start your function
 
 function contains(object, key) {
-  if (Array.isArray(object) && Object.keys(object).length === 0) {
+  // Reject arrays, null, or non-object types
+  if (object === null || typeof object !== "object" || Array.isArray(object)) {
     return false;
-  } else if (object.hasOwnProperty(key)) {
-    return true;
-  } else return false;
+  }
+
+  // Safely check if the object has the property
+  return Object.prototype.hasOwnProperty.call(object, key);
 }
 
 let key = "name";
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 2713519ca..8e7015468 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -63,3 +63,35 @@ test("It return false when an array is passed instead of object", () => {
   let key = "name";
   expect(contains(object, key)).toEqual(false);
 });
+
+// New testes after receiving feedback ==>
+
+test("It return false when null is passed instead of object", () => {
+  let object = null;
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});
+
+test("It return false when undefined is passed instead of object", () => {
+  let object = undefined;
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});
+
+test("It return false when a number is passed instead of object", () => {
+  let object = 123;
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});
+
+test("It return false when a string is passed instead of object", () => {
+  let object = "hello";
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});
+
+test("It return false when a boolean is passed instead of object", () => {
+  let object = true;
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});

From 17557e23c85f6e699165b1d326ea78e42c4b58d4 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Sun, 22 Mar 2026 19:23:05 +0000
Subject: [PATCH 08/11] replaced let with const in createLookup function

---
 Sprint-2/implement/lookup.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index 0a01c5652..d587847ab 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,9 +1,9 @@
 // start your function;
 function createLookup(input) {
-  let output = {};
+  const output = {};
   for (let pair of input) {
-    let key = pair[0];
-    let value = pair[1];
+    const key = pair[0];
+    const value = pair[1];
     output[key] = value;
   }
   return output;

From f5ad08e16d6725b4a6aaacde57ea19f14fa32c56 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Sun, 22 Mar 2026 19:42:58 +0000
Subject: [PATCH 09/11] tally function and jest tests updated

---
 Sprint-2/implement/tally.js      | 18 +++++++++---------
 Sprint-2/implement/tally.test.js | 30 ++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index 6cddd4258..a60936249 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,13 +1,13 @@
 function tally(arr) {
-  let output = {};
-  if (!Array.isArray(arr)) {
-    throw new Error("Invalid input");
-  } else if (arr.length === 0) {
-    return output;
-  }
-  for (let item of arr) {
-    let count = arr.filter((x) => x === item).length;
-    output[item] = count;
+  if (!Array.isArray(arr)) throw new Error("Invalid input");
+
+  const output = {};
+  for (const item of arr) {
+    if (output[item]) {
+      output[item] += 1; // increment count if already exists
+    } else {
+      output[item] = 1; // first occurrence
+    }
   }
   return output;
 }
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 9a0776f30..aa7a55d51 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -46,3 +46,33 @@ test("it throw an error if given a string", () => {
   const str = "a";
   expect(() => tally(str)).toThrowError();
 });
+// ===> new tests after feedback;
+// Invalid input: number
+test("it throw an error if given a number", () => {
+  let num = 123;
+  expect(() => tally(num)).toThrowError();
+});
+
+// Invalid input: null
+test("it throw an error if given null", () => {
+  let value = null;
+  expect(() => tally(value)).toThrowError();
+});
+
+// Invalid input: undefined
+test("it throw an error if given undefined", () => {
+  let value = undefined;
+  expect(() => tally(value)).toThrowError();
+});
+
+// Invalid input: boolean
+test("it throw an error if given a boolean", () => {
+  let value = true;
+  expect(() => tally(value)).toThrowError();
+});
+
+// Invalid input: object
+test("it throw an error if given an object instead of array", () => {
+  let obj = { a: 1 };
+  expect(() => tally(obj)).toThrowError();
+});

From 05d578c337025353420cb8c995dc3b5748124f83 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Mon, 23 Mar 2026 12:50:24 +0000
Subject: [PATCH 10/11] count-words and mode function have been refactored and
 updated

---
 Sprint-2/stretch/count-words.js | 13 +++++------
 Sprint-2/stretch/mode.js        | 38 +++++++++++++++++----------------
 2 files changed, 27 insertions(+), 24 deletions(-)

diff --git a/Sprint-2/stretch/count-words.js b/Sprint-2/stretch/count-words.js
index 78bd31ebf..c630040bf 100644
--- a/Sprint-2/stretch/count-words.js
+++ b/Sprint-2/stretch/count-words.js
@@ -29,14 +29,15 @@
 3. Order the results to find out which word is the most common in the input
 */
 function countWords(str) {
-  let cleanStr = str.split(" ");
-  let objWords = {};
+  const cleanStr = str.split(" ");
+  const objWords = Object.create(null); // object with no prototype;
   for (let word of cleanStr) {
-    if (word !== "") continue;
-    if (objWords[word]) {
-      objWords[word]++;
+    if (word === "") continue;
+    const lower = word.toLowerCase(); // normalize case
+    if (objWords[lower]) {
+      objWords[lower]++;
     } else {
-      objWords[word] = 1;
+      objWords[lower] = 1;
     }
   }
   return objWords;
diff --git a/Sprint-2/stretch/mode.js b/Sprint-2/stretch/mode.js
index 208b3f038..d2d633749 100644
--- a/Sprint-2/stretch/mode.js
+++ b/Sprint-2/stretch/mode.js
@@ -8,30 +8,32 @@
 // refactor calculateMode by splitting up the code
 // into smaller functions using the stages above
 
-function calculateMode(list) {
-  // Stage 1: Count frequencies
-  let freqs = {};
-  for (let num of list) {
-    if (typeof num !== "number") continue; // skip non-number values
-
-    if (freqs[num] === undefined) {
-      freqs[num] = 1;
-    } else {
-      freqs[num] += 1;
-    }
+function countFrequencies(list) {
+  const freqs = new Map(); // used Map instead of {}
+  for (const num of list) {
+    if (typeof num !== "number") continue;
+    freqs.set(num, (freqs.get(num) || 0) + 1);
   }
-  // Stage 2: Find the value with the highest frequency
+  return freqs;
+}
+
+function findMode(freqs) {
   let maxFreq = 0;
   let mode = null;
-
-  for (let num in freqs) {
-    if (freqs[num] > maxFreq) {
-      maxFreq = freqs[num];
-      mode = Number(num); // convert string key to number
+  for (const [num, freq] of freqs) {
+    if (freq > maxFreq) {
+      maxFreq = freq;
+      mode = num;
     }
   }
-
   return mode;
 }
 
+function calculateMode(list) {
+  const freqs = countFrequencies(list);
+  return findMode(freqs);
+}
+
+console.log(calculateMode([1, 2, 2, 3, 3, 3, 4])); // Output: 3
+
 module.exports = calculateMode;

From a76c37bad275319f86ec41d7f20a79f0d549ac08 Mon Sep 17 00:00:00 2001
From: RomanSanaye <sanaye143@gmail.com>
Date: Tue, 24 Mar 2026 09:54:54 +0000
Subject: [PATCH 11/11] Add test to ensure arrays are rejected in contains
 function

---
 Sprint-2/implement/contains.test.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 8e7015468..e46165b4c 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -58,9 +58,9 @@ test("It returns false when the object does NOT have the specified property", ()
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
-test("It return false when an array is passed instead of object", () => {
-  let object = [1, 2, 3];
-  let key = "name";
+test("It returns false even if array contains the key (arrays are invalid)", () => {
+  const object = [1, 2, 3];
+  const key = 0;
   expect(contains(object, key)).toEqual(false);
 });