Sheffield | 26-ITP-Jan | Seti Mussa | Sprint 2 | Data Group

Sprint-2/debug/address.js

@@ -1,4 +1,6 @@
 // Predict and explain first...
+//Its will say undefined. This is because the address object does not have an index of 0.
+// To access the houseNumber property of the address object, we need to use dot notation or bracket notation with the property name as a string
 
 // 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}`);

Sprint-2/debug/author.js

@@ -1,7 +1,8 @@
 // Predict and explain first...
-
+// It will throw a TypeError.Because a for of loop only can go throuhgh things like strings and arrays but not object.
 // 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
+// To print the value of the object , we use object.values() because it turn the object into list of value that er can loop through and log.
 
 const author = {
   firstName: "Zadie",
@@ -11,6 +12,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -1,9 +1,10 @@
 // Predict and explain first...
-
+// It will trown an error. However my perdiction was wrong it  doesn't throw errow ,instead it print the ingredients array and [ object object] 
+// because of the whole recipe object is being converted to string.
 // 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?
-
+// I fixed by used the join () method to print the each ingredient on new line.
 const recipe = {
   title: "bruschetta",
   serves: 2,
@@ -12,4 +13,4 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join('\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)) {
+    return false;
+  }
+
+  return Object.hasOwn(obj, prop);
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,16 +20,27 @@ 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({}, "a")).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 property exists", () => {
+  expect(contains({ a: 1, b: 2 }, "a")).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
-
+test("return false when property does not exit", () => {
+  expect(contains({ a: 1, b: 2 }, "c")).toBe(false);
+});
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("return false for invalid input like an array", () => {
+  expect(contains([1, 2, 3], "0")).toBe(false);
+});
+

Sprint-2/implement/lookup.js

@@ -1,5 +1,14 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  if (!Array.isArray(pairs)) return {};
+  const lookup = {};
+
+  for (const pair of pairs) {
+    if (!Array.isArray(pair) || pair.length !== 2) continue;
+
+    const [country, currency] = pair;
+    lookup[country] = currency;
+  }
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,33 @@
 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 result = createLookup(input);
+
+  expect(result).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
+test("returns an empty object for an empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+test("returns an empty object for invalid input", () => {
+  expect(createLookup("not-an-array")).toEqual({});
+});
+
+test("ignores invalid pairs inside array", () => {
+  const input = [["US", "USD"], ["CA"], "invalid"];
+
+  expect(createLookup(input)).toEqual({
+    US: "USD",
+  });
+});
 
 /*
 
@@ -15,6 +42,7 @@ Given
 When
  - createLookup function is called with the country-currency array as an argument
 
+
 Then
  - It should return an object where:
  - The keys are the country codes

Sprint-2/implement/querystring.js

@@ -1,12 +1,20 @@
 function parseQueryString(queryString) {
-  const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
+  if (typeof queryString !== "string" || queryString.length === 0) {
+    return {};
   }
+
+  const queryParams = {};
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    if (!pair) continue;
+
+    const index = pair.indexOf("=");
+    if (index === -1) continue;
+
+    const key = pair.slice(0, index);
+    const value = pair.slice(index + 1);
+
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -3,10 +3,32 @@
 // 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("returns empty object for empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("returns empty object for empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses multiple key value pairs", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({
+    a: "1",
+    b: "2",
+  });
+});
+
+test("ignores invalid pairs without =", () => {
+  expect(parseQueryString("a=1&invalid&b=2")).toEqual({
+    a: "1",
+    b: "2",
   });
 });

Sprint-2/implement/tally.js

@@ -1,3 +1,15 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("Expected an array");
+  }
+
+  const counts = Object.create(null);
+
+  for (const item of items) {
+    counts[item] = (counts[item] || 0) + 1;
+  }
+
+  return counts;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -1,5 +1,39 @@
 const tally = require("./tally.js");
 
+/**
+ * tally array
+ *
+ * In this task, you'll need to implement a function called tally
+ * that will take a list of items and count the frequency of each item
+ * in an arraynp
+ *
+ * For example:
+ *
+ * tally(['a']), target output: { a: 1 }
+ * tally(['a', 'a', 'a']), target output: { a: 3 }
+ * 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
+test("tally on an array with duplicate items returns correct counts", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+});
+
+// Given an empty array
+// When passed to tally
+// Then it should return 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
+
 /**
  * tally array
  *
@@ -19,16 +53,34 @@ 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("tally on an array with duplicate items returns correct counts", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 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("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 countss for each unique item", () => {
+  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 for invalid input", () => {
+  expect(() => tally("not-an-array")).toThrow();
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test(" tally throws an error for invalid input", () => {
+  expect(() => tally("not-an-array")).toThrow();
+});

Sprint-2/interpret/invert.js

@@ -17,13 +17,42 @@ function invert(obj) {
 }
 
 // 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}
+return { 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 needed so we can loop through the object and access both keys and values.
+Object.entries({ a: 1, b: 2 });
+// [["a", 1], ["b", 2]]
 
 // d) Explain why the current return value is different from the target output
-
+//The current output is wrong because invertedObj.key uses a fixed property name instead of the variable key, so it overwrites the same property each time.
+//It should use invertedObj[value] = key to properly swap keys and values.
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+const invert = require("./invert.js");
+
+test("inverts a normal object", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({
+    1: "a",
+    2: "b",
+  });
+});
+
+test("inverts a single pair", () => {
+  expect(invert({ x: 10 })).toEqual({
+    10: "x",
+  });
+});
+
+test("returns empty object when input is empty", () => {
+  expect(invert({})).toEqual({});
+});