Manchester| ITP-25-SEP | Fithi Teklom| Sprint 2 | Coursework

Sprint-2/debug/address.js

@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// After i run it will be undefined or throw an error because this is an object not an array to use the square bracket.
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -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 +1,5 @@
 // Predict and explain first...
-
+// Plain objects are not iterable so we have to use some of the built in object methods.
 // 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)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// I think I have to use index to log out every ingredient as it is an array.
 // 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 +10,9 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+
+console.log(`
+${recipe.title} serves ${recipe.serves}
+ingredients:
+${recipe.ingredients.join("\n")}
+`);

Sprint-2/implement/contains.js

@@ -1,3 +1,12 @@
-function contains() {}
+function contains(obj, key) {
+
+    if(typeof obj !== "object" || obj === null || Array.isArray(obj)){
+        return false;
+    }
+
+        return obj.hasOwnProperty(key);
+
+
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -8,7 +8,7 @@ E.g. contains({a: 1, b: 2}, 'a') // returns true
 as the object contains a key of 'a'
 
 E.g. contains({a: 1, b: 2}, 'c') // returns false
-as the object doesn't contains a key of 'c'
+as the object doesn't contain a key of 'c'
 */
 
 // Acceptance criteria:
@@ -20,16 +20,41 @@ 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 an empty object returns false", () => {
+  expect(contains({}, "a")).toBe(false);
+});
+
+// Given invalid parameters like an array
+// When passed to contains
+// Then it should return false or throw an error
+
+test("contains array-like object,invalid object and null  returns false",() => {
+    expect(contains([], "a")).toBe(false);
+    expect(contains(123, "a")).toBe(false);
+    expect(contains(null, "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 for existent property", () => {
+    const obj = {a: 1, b: 2}
+    expect(contains(obj, "a")).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 for non existent properties", () => {
+    const obj1= {a: 1, b:2}
+    expect(contains("c")).toBe(false);
+});
+
+
+
+
+
 
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error

Sprint-2/implement/lookup.js

@@ -1,5 +1,10 @@
-function createLookup() {
+function createLookup(pairs) {
   // implementation here
+  const lookup = {};
+  for(const [countryCode, currencyCode]of pairs){
+    lookup[countryCode] = currencyCode;
+  }
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,15 @@
 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 countryCurrencyPairs = [['US', 'USD'], ['CA', 'CAD']];
+
+     const expected = {
+    US: 'USD',
+    CA: 'CAD',
+     }
+     expect(createLookup(countryCurrencyPairs)).toEqual(expected);
+});
+
 
 /*
 

Sprint-2/implement/querystring.js

@@ -6,11 +6,19 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
-  }
 
-  return queryParams;
+    const idx = pair.indexOf("=");
+
+    if (idx === -1) {
+         const key = decodeURIComponent(pair.replace(/\+/g, " "));
+      queryParams[key] = "";
+    }  else {
+      const key = decodeURIComponent(pair.substring(0, idx).replace(/\+/g, " "));
+      const value = decodeURIComponent(pair.substring(idx + 1).replace(/\+/g, " "));
+      queryParams[key] = value;
+    }
+}
+return queryParams;
 }
 
 module.exports = parseQueryString;

Sprint-2/implement/querystring.test.js

@@ -3,10 +3,30 @@
 // 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",
   });
 });
+test("parses empty values", () =>{
+  expect(parseQueryString("a=&b=2")).toEqual({a:"",b:"2"})
+});
+
+test("parses containing =",() => {
+  expect(parseQueryString("equation=x=y+1")).toEqual({equation: "x=y+1"})
+});
+
+
+test("parses empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses multiple pairs including empty value", () => {
+  expect(parseQueryString("a=1&b=&c=3")).toEqual({ a: "1", b: "", c: "3" });
+});
+
+test("parses repeated keys (last one wins)", () => {
+  expect(parseQueryString("a=1&a=2")).toEqual({ a: "2" });
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,20 @@
-function tally() {}
+function tally(items) {
+     if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  const result = Object.create(null);;
+
+  for (const item of items) {
+    if (result[item]) {
+      result[item] += 1;
+    } else {
+      result[item] = 1;
+    }
+  }
+
+  return result;
+
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,12 +23,34 @@ 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");
 
+
+// Empty array → empty object
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
+
+
+test("tally counts occurrences of items", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({
+    a: 2,
+    b: 1,
+    c: 1
+  });
+});
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("tally works for a single repeated item", () => {
+  expect(tally(["x", "x", "x"])).toEqual({ x: 3 });
+});
 
 // 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("Input must be an array");
+});
+
+
+

Sprint-2/interpret/invert.js

@@ -7,23 +7,36 @@
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
 function invert(obj) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    throw new Error("Input must be a non-null object");
+  }
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    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 }
+//Only the last value remains, so it returns:
+//{ 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?
+// as it is a built in method Object.entries returns an array of [key, value] pairs.
+//It is needed so we can loop through both keys and values easily.
 
 // d) Explain why the current return value is different from the target output
+//Because the code uses invertedObj.key (a literal property named "key") instead of using the variable key.
+//It overwrites the same property instead of swapping keys and values
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,28 @@
+const invert = require("./invert");
+
+test("inverts a simple object", () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+test("inverts multiple key/value pairs", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ "1": "a", "2": "b" });
+});
+
+test("inverts string values", () => {
+  expect(invert({ x: "apple", y: "banana" })).toEqual({
+    apple: "x",
+    banana: "y"
+  });
+});
+
+test("throws an error when input is not an object", () => {
+  expect(() => invert("not an object")).toThrow("Input must be a non-null object");
+});
+
+test("throws an error for null", () => {
+  expect(() => invert(null)).toThrow("Input must be a non-null object");
+});
+
+test("throws an error for arrays", () => {
+  expect(() => invert([1, 2, 3])).toThrow("Input must be a non-null object");
+});

Sprint-2/package.json

@@ -6,10 +6,15 @@
   "scripts": {
     "test": "jest"
   },
+  "type": "module",
   "keywords": [],
   "author": "",
   "license": "ISC",
   "devDependencies": {
     "jest": "^29.7.0"
-  }
+  },
+  "editor.defaultFormatter": "esbenp.prettier-vscode",
+  "editor.formatOnSave": true,
+  "prettier.singleQuote": true,
+  "prettier.trailingComma": "es5"
 }

Sprint-2/stretch/count-words.js

@@ -26,3 +26,33 @@
 
 3. Order the results to find out which word is the most common in the input
 */
+function countWords(str){
+ str = str.toLowerCase();
+
+  // 2. Remove punctuation (anything that is not a letter, number, or space)
+  str = str.replace(/[^\w\s]/g, '');
+
+  // 3. Split the string into words
+  const words = str.split(/\s+/);
+
+  // 4. Create an object to store word counts
+  const wordCounts = {};
+
+  // 5. Count each word
+  for (const word of words) {
+    if (word === '') continue; // skip empty strings (in case of multiple spaces)
+    if (wordCounts[word]) {
+      wordCounts[word] += 1;
+    } else {
+      wordCounts[word] = 1;
+    }
+  }
+
+  // 6. Optional: Sort by frequency (most common first)
+  const sortedWordCounts = Object.fromEntries(
+    Object.entries(wordCounts).sort((a, b) => b[1] - a[1])
+  );
+  return sortedWordCounts;
+};
+
+console.log(countWords("You and me, and you!"));