WESTMIDLANDS|MAY-2025|SARA TAHIR|Sprint 2/coursework

Sprint-2/debug/address.js

@@ -12,4 +12,7 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address.houseNumber}`);
+//It will not work because we cannot access a keys value from an object through index position.
+//Fixed the code by using dot notation with the variable and the key. 
+// The current code is correctly giving us the output for the housenumber.

Sprint-2/debug/author.js

@@ -10,7 +10,12 @@ const author = {
   age: 40,
   alive: true,
 };
-
-for (const value of author) {
-  console.log(value);
+function readvalues(){
+for (const key in author) {
+  console.log(key + ':' +author[key]);
+}
 }
+readvalues();
+/* My first  prediction was that it wont work and we will need a for of loop to iterate over every key in object.
+ That prediction failed because a for of loop doesn't work here. we need a for in loop or we can also use a built in js method 
+ called object.keys(), for my  better understanding I will use a for in loop here.*/

Sprint-2/debug/recipe.js

@@ -10,6 +10,15 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+console.log(`${recipe.title} serves ${recipe.serves}\ningredients:`); // add a line break
+recipe.ingredients.forEach((ingredient) => { //iterate over ear ingredient in ingredients.
+  console.log(ingredient);
+})
+/* This will log the whole object recipe rather than each ingredient on a different line.
+We need to access each item of ingredients from the array seperately.Iterate over them.
+we could also use 
+console.log(`${recipe.title} serves ${recipe.serves}\ningredients:`);
+
+for (let i = 0; i < recipe.ingredients.length; i++) {
+  console.log(recipe.ingredients[i]);
+}*/ 

Sprint-2/implement/contains.js

@@ -1,3 +1,16 @@
-function contains() {}
+function contains(object, propertyName) {
+  // Check if the input is a real object (not null or an array)
+  const isObject =
+    typeof object === "object" && object !== null && !Array.isArray(object);
+
+  // If it's not a valid object or property name is missing, return false
+  if (!isObject || typeof propertyName !== "string") {
+    return false;
+  }
+
+  // Return true if the object has the property directly (not inherited)
+  return object.hasOwnProperty(propertyName);
+}
+
 
 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");
+
+test("contains on empty object returns false",function(){
+const input = {}
+const result = contains(input,"name")
+expect(result).toBe(false)
+});
+
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
-
+test("returns true when object contains the property 'name'",function(){
+const input ={firstName: "Sara",lastName: "Tahir",}
+const result= contains(input, "firstName")
+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("returns false when object doesn't contain the property 'name'",function(){
+const input ={firstName: "Sara",lastName: "Tahir",}
+const result= contains(input, "address")
+expect(result).toBe(false)
+})
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("returns false when an array is passed instead of an object", function () {
+  const input = ["address"];
+  const result = contains(input, "address");
+  expect(result).toBe(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,25 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  const lookup = {};
+  for (let i = 0; i < pairs.length; i++) {
+    const [country, currency] = pairs[i];
+    lookup[country] = currency;
+  }
+  return lookup;
 }
-
+  
 module.exports = createLookup;
+
+/*const pair = [['US','USD'],['CA','CAD']]
+  const firstpair = pair[0]
+  let country1 = firstpair[0]
+  let currency1 = firstpair[1]
+  console.log("First country:", country1);     // US
+  console.log("First currency:", currency1); 
+
+  const secondPair= pair[1]
+  let country2 = secondPair[0]
+  let currency2 = secondPair[1]
+  console.log("Second country:", country2);    // CA
+  console.log("Second currency:", currency2);
+}
+*/

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,11 @@
 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'],['PAK','PKR']];
+  const expected = { 'US': 'USD', 'CA': 'CAD','PAK':'PKR' };
+  const result = createLookup(input);
+  expect(result).toEqual(expected);
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -1,16 +1,49 @@
+
 function parseQueryString(queryString) {
   const queryParams = {};
+
+
+  if (queryString.startsWith("?")) { // Remove "?" if present at start 
+    queryString = queryString.substring(1);
+  }
+
   if (queryString.length === 0) {
     return queryParams;
   }
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (!pair) continue; // Skip empty strings from && or trailing &,
+
+    const idx = pair.indexOf("=");
+
+    let rawKey, rawValue;
+
+    if (idx === -1) {
+      rawKey = pair;
+      rawValue = "";
+    } else {
+      rawKey = pair.slice(0, idx);// starts at zero, stop just before the index of =
+      rawValue = pair.slice(idx + 1);
+    }
+
+    // Decode without replacing '+' with space
+    const key = decodeURIComponent(rawKey);
+    const value = decodeURIComponent(rawValue);
+
+    if (queryParams.hasOwnProperty(key)) {
+      if (Array.isArray(queryParams[key])) {
+        queryParams[key].push(value);
+      } else {
+        queryParams[key] = [queryParams[key], value];
+      }
+    } else {
+      queryParams[key] = value;
+    }
   }
 
   return queryParams;
 }
-
+    
 module.exports = parseQueryString;

Sprint-2/implement/querystring.test.js

@@ -10,3 +10,42 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+test("parses empty query string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("ignores leading question mark", () => {
+  expect(parseQueryString("?name=Sara")).toEqual({ name: "Sara" });
+});
+
+test("parses multiple key-value pairs", () => {
+  expect(parseQueryString("name=Sara&age=30")).toEqual({
+    name: "Sara",
+    age: "30"
+  })
+});
+
+test("handles missing value", () => {
+  expect(parseQueryString("name=")).toEqual({ name: "" });
+});
+
+test("handles missing key", () => {
+  expect(parseQueryString("=value")).toEqual({ "": "value" });
+});
+
+test("handles key without =", () => {
+  expect(parseQueryString("flag")).toEqual({ flag: "" });
+});
+
+test("handles duplicate keys", () => {
+  expect(parseQueryString("id=1&id=2")).toEqual({ id: ["1", "2"] });
+});
+test("decodes URL-encoded characters", () => {
+  expect(parseQueryString("name=Sara%20Tahir&city=Nottingham%20City")).toEqual({
+    name: "Sara Tahir",
+    city: "Nottingham City"
+  });
+});
+test("handles empty key and value", () => {
+  expect(parseQueryString("=")).toEqual({ "": "" });
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,21 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("Input should be an array");
+  }
 
+  const result = {};
+
+  for (const item of items) {
+    if (result[item]) {
+      result[item]++;
+    } else {
+      result[item] = 1;
+    }
+  }
+
+  return result;
+}
 module.exports = tally;
+//takes and array of items
+//item are keys
+// how many times that item is repeated in the array- count of that item(key) is the value of each key 

Sprint-2/implement/tally.test.js

@@ -14,21 +14,45 @@ const tally = require("./tally.js");
  * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
  */
 
-// Acceptance criteria:
-
-// Given a function called tally
-// When passed an array of items
-// Then it should return an object containing the count for each unique item
-
 // 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 one item
+// When passed to tally
+// Then it should return an object with count 1 for that item
+test("tally on an array with one item returns correct count", () => {
+  expect(tally(['a'])).toEqual({ a: 1 });
+});
 
 // 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 correct counts", () => {
+  expect(tally(['a', 'a', 'a'])).toEqual({ a: 3 });
+  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 an error on invalid input like a string", () => {
+  expect(() => tally("invalid input")).toThrow();
+});
+
+// Given an invalid input like a number
+// When passed to tally
+// Then it should throw an error
+test("tally throws an error on invalid input like a number", () => {
+  expect(() => tally(123)).toThrow();
+});
+
+// Given an invalid input like null
+// When passed to tally
+// Then it should throw an error
+test("tally throws an error on invalid input like null", () => {
+  expect(() => tally(null)).toThrow();
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,37 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
+let object = {a:1,b:2}
+console.log((invert)(object))
 
+module.exports= invert
 // a) What is the current return value when invert is called with { a : 1 }
+// Current return value is {key: 1}, I was expecting {"1":"a"}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+//// Current return value is {key: 2}, I was expecting {"1":"a", "2":"b"}
 
 // 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 is creating an array of key-value pairs.
 
 // d) Explain why the current return value is different from the target output
+/*The target output swaps the keys and values. But in the current function,
+ the line invertedObj.key = value creates a property named "key" literally, 
+ instead of using the variable key from the key-value pair. 
+ This means it doesn’t use the actual key from the object, so the output is wrong.
+ To swap keys and values properly, we need to use bracket notation (invertedObj[value] = key) 
+ so that the value of the variable value is used as the property name.
+
+*/
+
+
+
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,17 @@
+const invert = require("./invert");
+
+test("given an object of key-value, it should return inverted value-key", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ "1": "a", "2": "b" });
+});
+
+test("given an object of single key-value, it should return single value-key", () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+test("given an empty input it should return an empty object", () => {
+  expect(invert({})).toEqual({});
+});
+
+test("invert values that are strings", () => {
+  expect(invert({ a: "1", b: "pink" })).toEqual({ "1": "a", "pink": "b" });
+});