Birmingham | ITP Jan 2026 | Arunkumar Akilan | Sprint 2 | Data Groups

Sprint-2/debug/address.js

@@ -12,4 +12,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address["houseNumber"]}`);

Sprint-2/debug/author.js

@@ -1,5 +1,6 @@
 // Predict and explain first...
-
+// The program throws an error because a for...of loop only works with iterable values like arrays or strings.
+// The author variable is an object, which is not iterable by default, so JavaScript cannot loop through it.
 // 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
 
@@ -10,7 +11,7 @@ const author = {
   age: 40,
   alive: true,
 };
-
-for (const value of author) {
-  console.log(value);
+const values = Object.values(author);
+for (const item of values) {
+  console.log(item);
 }

Sprint-2/debug/recipe.js

@@ -1,5 +1,6 @@
 // Predict and explain first...
-
+//The title and serves values print correctly because the properties are accessed directly using
+// recipe.title and recipe.serves.
 // 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 +11,10 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+console.log(`${recipe.title} serves ${recipe.serves}`);
+for (const ingredients of recipe.ingredients) {
+  console.log(`*${ingredients}`);
+}
+
+//The program prints the recipe title and number of servings.
+// Then it loops through the ingredients array and logs each ingredient on a new line so they are displayed individually instead of printing the whole object.

Sprint-2/implement/contains.js

@@ -1,3 +1,14 @@
-function contains() {}
+function contains(object, propertyName) {
+  if (typeof object !== "object" || Array.isArray(object) || object === null) {
+    throw new Error("It is a invalid object");
+  }
+  const newArray = Object.keys(object);
+  for (let item of newArray) {
+    if (item === propertyName) {
+      return true;
+    }
+  }
+  return false;
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -11,6 +11,37 @@ E.g. contains({a: 1, b: 2}, 'c') // returns false
 as the object doesn't contains a key of 'c'
 */
 
+test("An empty object should return false", () => {
+  const object = {};
+  const propertyName = "a";
+  expect(contains(object, propertyName)).toEqual(false);
+});
+
+test("returns true when the object contains an existing property name", () => {
+  const object = { a: 1, b: 2, c: 3 };
+  const propertyName = "a";
+  expect(contains(object, propertyName)).toEqual(true);
+});
+test("returns false when the object not contains an existing property name", () => {
+  const object = { a: 1, b: 2, c: 3 };
+  const propertyName = "d";
+  expect(contains(object, propertyName)).toEqual(false);
+});
+test("Should throw an error for an invalid parameters", () => {
+  const object = [1, 2, 3, 4, 5, 6, 7];
+  const propertyName = "a";
+  expect(() => contains(object, propertyName)).toThrow();
+});
+test("Should throw an error for an invalid parameters", () => {
+  const object = null;
+  const propertyName = "a";
+  expect(() => contains(object, propertyName)).toThrow();
+});
+test("Should throw an error for an invalid parameters", () => {
+  const object = "hi";
+  const propertyName = "a";
+  expect(() => contains(object, propertyName)).toThrow();
+});
 // Acceptance criteria:
 
 // Given a contains function

Sprint-2/implement/lookup.js

@@ -1,5 +1,11 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  const countryCurrencyLookup = {};
+
+  for (let item of countryCurrencyPairs) {
+    const [key, value] = [item[0], item[1]];
+    countryCurrencyLookup[key] = value;
+  }
+  return countryCurrencyLookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -2,6 +2,20 @@ const createLookup = require("./lookup.js");
 
 test.todo("creates a country currency code lookup for multiple codes");
 
+test("An array of arrays representing country code and currency code should return an object where the keys are country code values are currency code", () => {
+  const countryCurrencyPairs = [
+    ["IND", "INR"],
+    ["US", "USD"],
+    ["UK", "GBR"],
+    ["CA", "CAD"],
+  ];
+  expect(createLookup(countryCurrencyPairs)).toEqual({
+    IND: "INR",
+    US: "USD",
+    UK: "GBR",
+    CA: "CAD",
+  });
+});
 /*
 
 Create a lookup object of key value pairs from an array of code pairs

Sprint-2/implement/querystring.js

@@ -5,8 +5,11 @@ function parseQueryString(queryString) {
   }
   const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+  for (const item of keyValuePairs) {
+    const pair = item.split("=");
+    const key = pair.shift();
+    const value = pair.join("=");
+    if (!key) continue;
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -3,10 +3,52 @@
 // 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",
   });
 });
+test("An empty string should return an empty object", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+test("parses querystring parameters with an empty value", () => {
+  expect(parseQueryString("name=")).toEqual({ name: "" });
+});
+test("handles querystring parameters that have no = sign", () => {
+  expect(parseQueryString("flag")).toEqual({ flag: "" });
+});
+test("parses querystring values containing multiple = characters", () => {
+  expect(parseQueryString("token=a=b=c=d")).toEqual({ token: "a=b=c=d" });
+});
+test("handles multiple querystring parameters when one value contains =", () => {
+  expect(parseQueryString("a=1&equation=x=y+1")).toEqual({
+    a: "1",
+    equation: "x=y+1",
+  });
+});
+test("ignores pairs with missing key (=b)", () => {
+  expect(parseQueryString("=b")).toEqual({});
+});
+
+test("ignores empty pairs (double &&)", () => {
+  expect(parseQueryString("a=b&&c=d")).toEqual({
+    a: "b",
+    c: "d",
+  });
+});
+test("ignores empty key and value (=)", () => {
+  expect(parseQueryString("=")).toEqual({});
+});
+test("ignores invalid pairs but keeps valid ones", () => {
+  expect(parseQueryString("a=b&=&c=d")).toEqual({
+    a: "b",
+    c: "d",
+  });
+});
+test("keeps key with empty value", () => {
+  expect(parseQueryString("a=")).toEqual({
+    a: "",
+  });
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,15 @@
-function tally() {}
+function tally(arr) {
+  const object = Object.create(null);
+  if (!Array.isArray(arr)) {
+    throw new Error("Invalid input: tally expects an array");
+  }
+  if (arr.length === 0) {
+    return object;
+  }
+  arr.forEach((ele) => {
+    object[ele] = (object[ele] || 0) + 1;
+  });
+  return object;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -13,6 +13,18 @@ const tally = require("./tally.js");
  * tally(['a', 'a', 'a']), target output: { a: 3 }
  * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
  */
+test("throws an error when the input is not an array", () => {
+  expect(() => tally("hi")).toThrow();
+});
+test("returns an empty object when the input array is empty", () => {
+  expect(tally([])).toEqual({});
+});
+test("returns the count of each unique item in the array", () => {
+  expect(tally(["a", "b", "a", "c", "b", "a"])).toEqual({ a: 3, b: 2, c: 1 });
+});
+test("handles special keys like toString", () => {
+  expect(tally(["toString", "toString"])).toEqual({ "toString": 2 });
+});
 
 // Acceptance criteria:
 
@@ -23,7 +35,7 @@ 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");
+
 
 // Given an array with duplicate items
 // When passed to tally

Sprint-2/interpret/invert.js

@@ -9,21 +9,28 @@
 function invert(obj) {
   const invertedObj = {};
 
-  for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+  for (const [key, value ] of Object.entries(obj)) {
+    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:1, 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?
+// Object.entries() returns an array of [key, value] pairs from an object. It is used here to loop through the object and access both the key and value in each iteration.
 
 // d) Explain why the current return value is different from the target output
+// The return value is different because the program uses dot notation with a variable instead of bracket notation.
+//  Also, the object needs to be inverted, so the key and value must be swapped when iterating through the entries.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,9 @@
+const invert = require("./invert");
+
+test("returns an object with the key and value swapped when given a single key-value pair", () => {
+  expect(invert({ a: 1 })).toEqual({ 1: "a" });
+});
+
+test("returns an object with all keys and values swapped for multiple key-value pairs", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ 1: "a", 2: "b" });
+});