London | May-2025 | KhilolaRustamova | Sprint 2 | Sprint 2 coursework

Sprint-2/debug/address.js

@@ -1,5 +1,9 @@
 // Predict and explain first...
 
+//The code is trying to access address[0], but address is an object, not an array.
+//Objects use keys (like houseNumber) instead of numeric indices.
+//So address[0] is undefined, because there is no property with the key "0".
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +16,8 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address.houseNumber}`);
+
+// The code is correct and will log "My house number is 42" to the console.
+
+// My house number is 42

Sprint-2/debug/author.js

@@ -1,5 +1,10 @@
 // Predict and explain first...
 
+//This code tries to use a for...of loop on an object, but objects are not iterable by default.
+//for...of works on iterables like arrays, strings, maps, sets — not plain objects.
+//Running this will throw:
+//TypeError: author is not iterable
+
 // 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 +16,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -1,4 +1,7 @@
 // Predict and explain first...
+//${recipe} tries to insert the entire object (recipe) directly into the string.
+//This will result in something like:[object Object]
+
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -10,6 +13,9 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
+console.log(`${recipe.title} 
+  serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`);
+//recipe.ingredients is an array: ["olive oil", "tomatoes", "salt", "pepper"]
+//.join("\n") turns that array into a string, separating each ingredient with a newline (\n)

Sprint-2/implement/contains.js

@@ -1,3 +1,9 @@
-function contains() {}
+function contains(obj, prop) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    throw new Error("Invalid input: must be a non-null object");
+  }
 
-module.exports = contains;
+  return obj.hasOwnProperty(prop);
+}
+
+module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,16 +20,35 @@ 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");
+
+// Empty object should return false
+test("contains on empty object returns false", () => {
+  const result = contains({}, "a");
+  expect(result).toBe(false); });
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
 
+// Object with properties and existing key should return true
+test("contains returns true for existing property", () => {
+  const obj = { a: 1, b: 2 };
+  const result = contains(obj, "a");
+  expect(result).toBe(true);
+});
+
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("contains returns false for non-existing property", () => {
+const obj = { a: 1, b: 2 };
+  const result = contains(obj, "c");
+  expect(result).toBe(false);
+ });
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("contains returns false or throws when input is not an object", () => {
+  const obj = ["a", "b"];
+   expect(() => contains(["a", "b"], "a")).toThrow(); });

Sprint-2/implement/lookup.js

@@ -1,4 +1,10 @@
-function createLookup() {
+function createLookup(pairs) {
+  const lookup= {};
+ for (let [countryCode, currencyCode] of pairs) {
+    lookup[countryCode] = currencyCode;
+  }
+
+  return lookup;
   // implementation here
 }
 

Sprint-2/implement/lookup.test.js

@@ -1,16 +1,57 @@
 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'],
+    ['UK', 'GBP'],
+  ];
+  const expected = {
+    US: 'USD',
+    CA: 'CAD',
+    UK: 'GBP'
+  };
+ expect(createLookup(input)).toEqual(expected);
+});
 
-/*
+test("returns an empty object when given an empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+test("overwrites value if a country code appears more than once", () => {
+  const input = [
+    ['UK', 'GBP'],
+    ['UK', 'POUND']
+  ];
+  expect(createLookup(input)).toEqual({ UK: 'POUND' });
+});
+
+test("ignores extra values in pairs", () => {
+  const input = [
+    ['UK', 'GBP', 'Extra'],
+    ['US', 'USD']
+  ];
+  expect(createLookup(input)).toEqual({ UK: 'GBP', US: 'USD' });
+});
+
+test("ignores invalid pairs (less than two elements)", () => {
+  const input = [
+    ['UK'], // Invalid
+    ['US', 'USD']
+  ];
+  expect(createLookup(input)).toEqual({ US: 'USD' });
+});
+
+
+  /*
 
 Create a lookup object of key value pairs from an array of code pairs
 
 Acceptance Criteria:
 
 Given
  - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
+   e.g. [['US', 'USD'], ['CA', 'CAD'],['UK','GBP']]
 
 When
  - createLookup function is called with the country-currency array as an argument
@@ -21,7 +62,7 @@ Then
  - The values are the corresponding currency codes
 
 Example
-Given: [['US', 'USD'], ['CA', 'CAD']]
+Given: [['US', 'USD'], ['CA', 'CAD'], ['UK', 'GPB']]
 
 When
 createLookup(countryCurrencyPairs) is called
@@ -30,6 +71,7 @@ Then
 It should return:
  {
    'US': 'USD',
-   'CA': 'CAD'
+   'CA': 'CAD',
+   'UK': 'GBP'
  }
 */

Sprint-2/implement/querystring.js

@@ -1,15 +1,18 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
-  }
+  if (!queryString) return queryParams;
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
-  }
+   const [key, ...rest] = pair.split("="); // Grab everything after first '='
+   const value = rest.join("="); // Safely join back if value had '=' signs
+
+   const decodedKey = decodeURIComponent((key || "").replace(/\+/g, " "));
+   const decodedValue = decodeURIComponent((value || "").replace(/\+/g, " "));
 
+    queryParams[decodedKey] = decodedValue;
+  }
   return queryParams;
 }
 

Sprint-2/implement/querystring.test.js

@@ -5,8 +5,36 @@
 
 const parseQueryString = require("./querystring.js")
 
-test("parses querystring values containing =", () => {
-  expect(parseQueryString("equation=x=y+1")).toEqual({
+test("parses querystring values containing +", () => {
+  expect(parseQueryString("equation=x%3Dy%2B1")).toEqual({
     "equation": "x=y+1",
   });
 });
+  test("returns empty object for empty query string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses single key with empty value", () => {
+  expect(parseQueryString("foo=")).toEqual({ foo: "" });
+});
+
+test("parses single key with no equals sign", () => {
+  expect(parseQueryString("foo")).toEqual({ foo: "" });
+});
+
+test("parses multiple key-value pairs", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({ a: "1", b: "2" });
+});
+
+test("decodes URL-encoded characters", () => {
+  expect(parseQueryString("name=John%20Doe&city=New%20York")).toEqual({
+    name: "John Doe",
+    city: "New York",
+  });
+});
+
+test("parses values containing =", () => {
+  expect(parseQueryString("token=abc=123")).toEqual({
+    token: "abc=123"
+  });
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,23 @@
-function tally() {}
+function tally(items) {
+  // Validate input: must be an array
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  // Create an object to hold counts
+  const counts = {};
+
+  // Loop through each item and count occurrences
+  for (const item of items) {
+    if (counts[item]) {
+      counts[item] += 1;
+    } else {
+      counts[item] = 1;
+    }
+  }
+
+  return counts;
+}
 
 module.exports = tally;
+

Sprint-2/implement/tally.test.js

@@ -23,12 +23,23 @@ 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 counts each unique item correctly", () => {
+  expect(tally(["a", "a", "b", "c"])).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("tally throws error on non-array input", () => {
+  expect(() => tally("not-an-array")).toThrow("Input must be an array");
+});

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;
 }
 
+console.log(invert({ a: 1, b: 2 })); 
 // a) What is the current return value when invert is called with { a : 1 }
+// { key: 1 }
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// { key: 2 }
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// { '1': 'a', '2': 'b' }
 
 // c) What does Object.entries return? Why is it needed in this program?
+//This is a built-in JavaScript method that takes an object and returns an array of key-value pairs as arrays.
 
 // d) Explain why the current return value is different from the target output
+// it is different because current code is not doing what we was expecting.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+module.exports = invert;

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,7 @@
+const invert = require("./invert.js");
+
+test("inverts a simple object with unique values", () => {
+  const input = { a: 1, b: 2 };
+  const expectedOutput = { 1: "a", 2: "b" };
+  expect(invert(input)).toEqual(expectedOutput);
+});