London | 25-ITP-Sep| Sophia Mohamed | Sprint 2 | Sprint 2 Coursework

Sprint-2/debug/address.js

@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+//because this not an array we can not use index to access the value
+// we need to use the key name instead
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +15,4 @@ 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 +1,5 @@
 // Predict and explain first...
-
+// for .. of only works with iterable objects like arrays or strings. but author is an 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
 
@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {//This extracts the values into an array, and arrays ARE iterable, so the loop works.
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// if i want to access the ingredients and present each item on a new line i will use \ and the index of each item
 // 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?
@@ -11,5 +11,8 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:
+${recipe.ingredients[0]}
+${recipe.ingredients[1]}
+${recipe.ingredients[2]}
+${recipe.ingredients[3]}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,11 @@
-function contains() {}
+function contains(obj, key) {
+  if (!obj || typeof obj !== "object" || Array.isArray(obj)) {//check if we have an object and makes sure it's not an array
+    return false;
+  }
+  if (Object.keys(obj).length === 0) {
+    return false;
+  }
+  return key in obj;
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -16,20 +16,37 @@ as the object doesn't contains a key of 'c'
 // Given a contains function
 // When passed an object and a property name
 // Then it should return true if the object contains the property, false otherwise
-
+test("returns true for an existing property", () => {
+  const obj = { a: 1, b: 2 };
+  expect(contains(obj, "a")).toBe(true);
+});
 // 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("contains on object with existing property returns true", () => {
+  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("contains on object with non-existent property returns false", () => {
+  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("contains on invalid parameters returns false", () => {
+  expect(contains([], "a")).toBe(false);
+  expect(contains(null, "a")).toBe(false);
+  expect(contains(123, "a")).toBe(false);
+  expect(contains("hello", "a")).toBe(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,14 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  const lookup = {};//start with an empty object
+
+  for (const pair of pairs) {
+    const country = pair[0];// first element is country code
+    const currency = pair[1];// second element is currency code
+    lookup[country] = currency;
+  }
+
+  return lookup;
+
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,22 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("creates a lookup object from country-currency pairs", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const expected = {
+    US: "USD",
+    CA: "CAD",
+  };
+
+  expect(createLookup(input)).toEqual(expected);
+});
+
+test("returns an empty object when given an empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -1,16 +1,29 @@
 function parseQueryString(queryString) {
-  const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
+  const result = {};
+
+  if (!queryString) {
+    return result;
   }
-  const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+  const pairs = queryString.split("&");
+
+  for (const pair of pairs) {
+    const index = pair.indexOf("="); // find FIRST "="
+
+    if (index === -1) {
+      // no "=" found → key with empty value
+      result[pair] = "";
+    } else {
+      const key = pair.slice(0, index);
+      const value = pair.slice(index + 1); // everything after "="
+      result[key] = value;
+    }
   }
 
-  return queryParams;
+  return result;
 }
 
+
+
+
 module.exports = parseQueryString;

Sprint-2/implement/querystring.test.js

@@ -10,3 +10,28 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+
+test("parses a simple key=value pair", () => {
+  expect(parseQueryString("name=Ali")).toEqual({
+    name: "Ali",
+  });
+});
+
+test("parses multiple key=value pairs", () => {
+  expect(parseQueryString("name=Ali&age=30")).toEqual({
+    name: "Ali",
+    age: "30",
+  });
+});
+
+test("returns empty object for empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("handles keys without values", () => {
+  expect(parseQueryString("flag")).toEqual({
+    flag: "",
+  });
+});
+
+

Sprint-2/implement/tally.js

@@ -1,3 +1,12 @@
-function tally() {}
+function tally(arr) {
+    if (!Array.isArray(arr)) {// if it is not array (string or number throw an error message
+        throw new TypeError("Input must be an array");
+    }
+
+    return arr.reduce((counts, item) => {
+        counts[item] = (counts[item] || 0) + 1;// loops through the array and count 
+        return counts;
+    }, {});
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -24,11 +24,27 @@ const tally = require("./tally.js");
 // When passed to tally
 // Then it should return an empty object
 test.todo("tally on an empty array returns an empty object");
-
+test("returns an empty object for an empty array", () => {
+  expect(tally([])).toEqual({});
+});
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test.todo("tally counts each unique item in the array");
+test("counts how many times each item appears", () => {
+  expect(tally(["a", "b", "a", "c", "b", "a"])).toEqual({
+    a: 3,
+    b: 2,
+    c: 1,
+  });
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test.todo("tally throws an error for non-array input");
+test("throws an error if input is not an array", () => {
+  expect(() => tally("not an array")).toThrow(TypeError);
+  expect(() => tally(123)).toThrow(TypeError);
+  expect(() => tally({})).toThrow(TypeError);
+});

Sprint-2/interpret/invert.js

@@ -6,24 +6,73 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
-function invert(obj) {
-  const invertedObj = {};
+//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.key = value;
+  //}
+
+  //return invertedObj;
 
-  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}
+// c) What is the target return value when invert is called with {a : 1, b: 2} 
+//the target is to swap keys and values
+{ 
+  "1": "a",
+  "2": "b"
+}
 
 // c) What does Object.entries return? Why is it needed in this program?
-
+//it returns an arrays of pairs   
+[
+  ["a", 1],
+  ["b", 2]
+]
+// it loops through the keys and the value at the same time 
 // d) Explain why the current return value is different from the target output
+Object.entries({ a: 1, b: 2 })
+//current return value
+[
+  ["a", 1],
+  ["b", 2]
+]
+//It lets us easily loop through the keys and values
+
+//for (const [key, value] of Object.entries(obj))
+//Because you wrote:
+//invertedObj.key = value;
+//This literally creates a property named "key", not the value of the variable key.
+//i need bracket notation:
+//invertedObj[value] = key;
+//This sets the property using the variable.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+function invert(obj) {
+  const invertedObj = {};
+
+  for (const [key, value] of Object.entries(obj)) {
+    invertedObj[value] = key; 
+  }
+
+  return invertedObj;
+}
+console.log("Test 1:", invert({ a: 1 })); 
+console.log("Expected: { '1': 'a' }"); 
+console.log("-------------");
+
+console.log("Test 2:", invert({ a: 1, b: 2 }));
+console.log("Expected: { '1': 'a', '2': 'b' }");
+console.log("-------------");
+
+console.log("Test 3:", invert({}));
+console.log("Expected: {}");
+console.log("-------------");
+
+module.exports = invert;