diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..36d82085a 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,4 +1,6 @@
 // Predict and explain first...
+// As this is an object (key-value pairs), the elements cannot be accessed through indexing like array.
+// Values can be accessed through their relevant key
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +14,4 @@ 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..622620136 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,4 +1,6 @@
 // Predict and explain first...
+// As object is key-value pairs of data, it isn't exactly iterable like arrays.
+// We can loop over the keys or values of an object using Object.entries()
 
 // 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 +13,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const [key, value] of Object.entries(author)) {
   console.log(value);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..bd012af67 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,4 +1,5 @@
 // Predict and explain first...
+// It is not accessing the ingredients array correctly.
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -12,4 +13,17 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`);
+
+
+// approach 2
+
+// let msg = '';
+
+// for (const ingredient of recipe.ingredients) {
+//   msg += ingredient + '\n';
+// }
+
+// console.log(`${recipe.title} serves ${recipe.serves}
+//   ingredients:
+// ${msg}`);
\ No newline at end of file
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..977db9e6c 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,13 @@
-function contains() {}
+function contains(obj, x) {
+    for (const key in obj) {
+        if (Object.hasOwn(obj, key) && key == x) {
+            return true
+        }
+    }
+    return false
+}
 
 module.exports = contains;
+
+// Object.hasOwn(obj, key)
+// This ensures the property belongs directly to the object, not its prototype.
\ No newline at end of file
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..8d1bf7179 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,38 @@ 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({})).toStrictEqual(false)
+});
+
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
 
+test("contains on object with an existing property name returns true", () => {
+    expect(contains({a: 1, b: 2, c: 3}, 'c')).toStrictEqual(true);
+    expect(contains({name: "John Doe", job: "developer"}, 'job')).toStrictEqual(true)
+    expect(contains({color: "blue", size: "xxl", madeOf: "China"}, 'madeOf')).toStrictEqual(true);
+})
+
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
 
+test("contains on object with properties with non-existent property name return false", () => {
+    expect(contains({a: 1, b: 2, c: 3}, 'g')).toStrictEqual(false);
+    expect(contains({a: 1, b: 2, c: 3}, 'abc')).toStrictEqual(false);
+    expect(contains({name: "John Doe", age: 31}, 'job')).toStrictEqual(false);
+})
+
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+
+test("contains on invalid parameters returns false", () => {
+    expect(contains(["a", "b", "c"])).toStrictEqual(false);
+    expect(contains("I am a string")).toStrictEqual(false);
+    expect(contains(777)).toStrictEqual(false);
+})
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..c1911e518 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,5 @@
-function createLookup() {
-  // implementation here
+function createLookup(arr) {
+  return Object.fromEntries(arr);
 }
 
-module.exports = createLookup;
+module.exports = createLookup;
\ No newline at end of file
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..88517abf9 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 input = [['US', 'USD'], ['CA', 'CAD']];
+  const givenInput = createLookup(input);
+  const targetOutput = {US: 'USD', CA: 'CAD'};
+
+  expect(givenInput).toEqual(targetOutput);
+});
+
+test("creates a country currency code lookup for multiple codes", () => {
+  const input = [['AUS', 'AUD'], ['GB', 'GBP'], ['US', 'USD']];
+  const givenInput = createLookup(input);
+  const targetOutput = {AUS: 'AUD', GB: 'GBP', US: 'USD'};
+
+  expect(givenInput).toEqual(targetOutput);
+})
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..8eff0a700 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,12 +1,23 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
-  }
+
+  if (!queryString) return queryParams;
+
   const keyValuePairs = queryString.split("&");
 
+  // 1. with RegEx
+  // for (const pair of keyValuePairs) {
+  //   const [key, value] = pair.split(/=(.*)/s);
+  //   queryParams[key] = value;
+  // }
+
+  // 2. with substring method
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const index = pair.indexOf("=");
+
+    const key = pair.substring(0, index);
+    const value = pair.substring(index + 1);
+
     queryParams[key] = value;
   }
 
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..aadfbc025 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -9,4 +9,27 @@ test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
     "equation": "x=y+1",
   });
+  expect(parseQueryString("token=abc=123=xyz")).toEqual({
+    "token": "abc=123=xyz",
+  });
+  expect(parseQueryString("shop=myshop.myshopify.com")).toEqual({
+    "shop": "myshop.myshopify.com",
+  });
+});
+
+test("parses querystring values containing = and &", () => {
+  expect(parseQueryString("category=shoes&color=black&size=10")).toEqual({
+    category: "shoes", color: "black", size: "10"
+  });
+   expect(parseQueryString("page=2&limit=10")).toEqual({
+    page: "2", limit: "10"
+  });
+});
+
+test("parses querystring values containing +", () => {
+  expect(parseQueryString("q=javascript+array+methods")).toEqual({
+    q: "javascript+array+methods"
+  })
 });
+
+
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..c685bcc23 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,26 @@
-function tally() {}
+function tally(arr) {
+    if (Array.isArray(arr)) {
+
+        let countObj = {};
+    
+        for (const item of arr) {
+    
+            if (countObj[item]) {
+                countObj[item] = countObj[item] + 1;
+            } else {
+                countObj[item] = 1;
+            }
+        }
+        
+        return countObj;
+    }
+
+    else throw new Error("");
+}
 
 module.exports = tally;
+
+// console.log(tally(['a', 'a', 'a', 'a', 'a', 'b', 'c']));
+
+
+// tally(['a', 'a', 'a', 'a', 'a', 'b', 'c']), target output: { a : 5, b: 1, c: 1 }
\ No newline at end of file
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..e9870bbaa 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -23,12 +23,38 @@ 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 on an array with duplicate items returns the counts for each uniqe item", () => {
+    const input = ['a', 'a', 'b', 'c'];
+    const givenInput = tally(input);
+    const targetOutput = { a : 2, b: 1, c: 1 };
+
+    expect(givenInput).toEqual(targetOutput);
+})
+
+test("tally on an array with duplicate items returns the counts for each uniqe item", () => {
+    const input = ['a', 'a', 'bx', 'bx', 'b', 'b', 'b', 'b', 'c'];
+    const givenInput = tally(input);
+    const targetOutput = { a : 2, bx: 2, b: 4, c: 1 };
+
+    expect(givenInput).toEqual(targetOutput);
+})
+
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+
+test("tall on invalid input throws an error", () => {
+    expect(() => tally("I am a string")).toThrow();
+    expect(() => tally(777)).toThrow();
+    expect(() => tally(true)).toThrow();
+    expect(() => tally(undefined)).toThrow();
+    expect(() => tally(null)).toThrow();
+})
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..aa2989bf5 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,29 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
 // 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}
+      // { key: 2 }
 
 // c) What does Object.entries return? Why is it needed in this program?
+      // Object.entries() returns an array of a given object's own enumerable string-keyed property key-value pairs
+      // It is needed here in order to loop over each of the key-value pairs
 
 // d) Explain why the current return value is different from the target output
+      // It is because `.key `is used on object.
+      // Instead [] should be used
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+      // fixed the issue by using `invertedObj[value] = key`
+      // It is swaping the key and value in the returned object
\ No newline at end of file
diff --git a/Sprint-2/stretch/count-words.js b/Sprint-2/stretch/count-words.js
index 8e85d19d7..d5ff6209c 100644
--- a/Sprint-2/stretch/count-words.js
+++ b/Sprint-2/stretch/count-words.js
@@ -26,3 +26,26 @@
 
 3. Order the results to find out which word is the most common in the input
 */
+
+function countWords(str) {
+  const arr = str.replace(/[^a-zA-Z0-9\s]/g, '').toLowerCase().split(" ")
+
+  let countObj = {};
+
+  for (const item of arr) {
+    
+    if (countObj[item]) {
+      countObj[item] = countObj[item] + 1
+    } else {
+      countObj[item] = 1;
+    }
+  }
+
+  // `Object.entries()` converts object to array
+  const sortedArray = Object.entries(countObj).sort((a, b) => b[1] - a[1]);
+
+  // `Object.fromEntries()` coverts the sorted array to object
+  return Object.fromEntries(sortedArray);
+}
+
+console.log(countWords("you? and! me, and you. me me me me hello Me"));
diff --git a/Sprint-2/stretch/mode.js b/Sprint-2/stretch/mode.js
index 3f7609d79..90f0087d5 100644
--- a/Sprint-2/stretch/mode.js
+++ b/Sprint-2/stretch/mode.js
@@ -8,7 +8,7 @@
 // refactor calculateMode by splitting up the code
 // into smaller functions using the stages above
 
-function calculateMode(list) {
+function calculateFrequency(list) {
   // track frequency of each value
   let freqs = new Map();
 
@@ -19,6 +19,11 @@ function calculateMode(list) {
 
     freqs.set(num, (freqs.get(num) || 0) + 1);
   }
+  return freqs;
+}
+
+function calculateMode(list) {
+  const freqs = calculateFrequency(list);
 
   // Find the value with the highest frequency
   let maxFreq = 0;
diff --git a/Sprint-2/stretch/mode.test.js b/Sprint-2/stretch/mode.test.js
index ca33c28a3..a95ad7036 100644
--- a/Sprint-2/stretch/mode.test.js
+++ b/Sprint-2/stretch/mode.test.js
@@ -29,4 +29,11 @@ describe("calculateMode()", () => {
 
     expect(calculateMode(nums)).toEqual(3);
   });
+
+  test("ignores non-number values", () => {
+    const nums = "CYF";
+
+    expect(calculateMode(nums)).toEqual(NaN);
+  });
+
 });
diff --git a/Sprint-2/stretch/till.js b/Sprint-2/stretch/till.js
index 6a08532e7..af34480ef 100644
--- a/Sprint-2/stretch/till.js
+++ b/Sprint-2/stretch/till.js
@@ -8,10 +8,10 @@ function totalTill(till) {
   let total = 0;
 
   for (const [coin, quantity] of Object.entries(till)) {
-    total += coin * quantity;
+    total += Number(coin.slice(0, -1)) * Number(quantity);
   }
 
-  return `£${total / 100}`;
+  return `£${(total / 100).toFixed(2)}`;
 }
 
 const till = {
@@ -22,10 +22,15 @@ const till = {
 };
 const totalAmount = totalTill(till);
 
+module.exports = totalTill;
+
 // a) What is the target output when totalTill is called with the till object
+      // £NaN
 
 // b) Why do we need to use Object.entries inside the for...of loop in this function?
+      // to convert the given object into array
 
 // c) What does coin * quantity evaluate to inside the for...of loop?
+      // it converts different coins with different values into single pense
 
 // 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..e99695680
--- /dev/null
+++ b/Sprint-2/stretch/till.test.js
@@ -0,0 +1,29 @@
+const totalTill = require('./till');
+
+test("given an object of coins, returns the total amount in pounds", () => {
+  const till = {
+      "1p": 10,
+      "5p": 6,
+      "50p": 4,
+      "20p": 10,
+  };
+  const givenInput = totalTill(till);
+  const expectedOutcome = "£4.40";
+
+  expect(givenInput).toEqual(expectedOutcome);
+});
+
+test("given an object of coins, returns the total amount in pounds", () => {
+  const till = {
+      "1p": 10,
+      "5p": 6,
+      "50p": 4,
+      "20p": 10,
+      "2p": 2
+  };
+  const givenInput = totalTill(till);
+  const expectedOutcome = "£4.44";
+
+  expect(givenInput).toEqual(expectedOutcome);
+});
+