Glasgow | May-2025 | Salah Ahmed | Data Groups | Sprint 2

Sprint-2/debug/address.js

@@ -1,4 +1,10 @@
 // Predict and explain first...
+// This code is intended to log the house number from an address object.
+// However, it seems that the console log is not functioning as expected and the result is undefined.
+// The issue lies in the way the property is being accessed from the address object.
+// to fix this, we need to access the property using the correct key.
+
+
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +18,4 @@ 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

@@ -1,4 +1,9 @@
 // Predict and explain first...
+// This code is intended to log out all the property values in the `author` object.
+// However, it is not working because the `for...of` loop is designed to iterate
+// over iterable objects like arrays or strings, but the `author` object is a plain object
+// which is not iterable. To fix this, we can use `Object.values()` to get
+// an array of the object's values, which can then be iterated over with a `for...of` loop.
 
 // 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 +16,7 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const key in author) {
+  const value = author[key];
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -1,4 +1,9 @@
 // Predict and explain first...
+// This code is intended to log out the title, how many it serves, and the ingredients of a recipe.
+// However, it is not working correctly because the `console.log` statement is trying to log
+// the entire `recipe` object directly, which will not format the ingredients as expected.
+// Instead, we need to iterate over the `ingredients` array and log each ingredient on a new line.
+// To fix this, we can use a template literal to format the output and use `join` to create a string of ingredients separated by new lines.
 
 // 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 +15,6 @@ 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 +1,13 @@
-function contains() {}
+function contains(object, property) {
+    const keysArray = Object.keys(object); // Converts object keys to an array
+
+    for (let i = 0; i < keysArray.length; i++) {
+      if (keysArray[i] === property) {
+        return true;
+      }
+    }
+
+    return false; // Property wasn't found
+  }
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -16,20 +16,41 @@ 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("contains returns true for 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 returns false for empty object", () => {
+  const obj = {};
+  expect(contains(obj, 'a')).toBe(false);
+});
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
 
+test("contains returns true for existing property in object", () => {
+  const obj = { a: 1, b: 2 };
+  expect(contains(obj, 'b')).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-existent property in object", () => {
+  const obj = { a: 1, b: 2 };
+  expect(contains(obj, 'c')).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 for invalid parameters", () => {
+  const arr = [1, 2, 3];
+  expect(contains(arr, 'length')).toBe(false);
+});
+

Sprint-2/implement/lookup.js

@@ -1,5 +1,15 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  const result = {};
+  for (const [country, currency] of pairs) {
+    result[country] = currency;
+  }
+  return result;
 }
 
-module.exports = createLookup;
+
+// Example usage:
+ //const countryCurrencyPairs = [['US', 'USD'], ['CA', 'CAD']];
+ //const lookup = createLookup([['US', 'USD'],['CA', 'CAD']]);
+ //console.log(lookup); // { US: 'USD', CA: 'CAD' }
+
+ module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,7 +1,13 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
-
+test("createLookup returns an object with country codes as keys and currency codes as values", () => {
+  const countryCurrencyPairs = [['US', 'USD'], ['CA', 'CAD']];
+  const expectedLookup = {
+    'US': 'USD',
+    'CA': 'CAD'
+  };
+  expect(createLookup(countryCurrencyPairs)).toEqual(expectedLookup);
+});
 /*
 
 Create a lookup object of key value pairs from an array of code pairs

Sprint-2/implement/querystring.js

@@ -1,16 +1,26 @@
 function parseQueryString(queryString) {
-  const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
-  }
-  const keyValuePairs = queryString.split("&");
+  if (!queryString) return {};
+
+  const result = {};
+  const pairs = queryString.split("&");
+
+  for (const pair of pairs) {
+    const index = pair.indexOf("=");
+    let key, value;
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (index === -1) {
+      key = decodeURIComponent(pair);
+      value = "";
+    } else {
+      key = decodeURIComponent(pair.slice(0, index));
+      value = decodeURIComponent(pair.slice(index + 1));
+    }
+
+    result[key] = value;
   }
 
-  return queryParams;
+  return result;
 }
 
+
 module.exports = parseQueryString;

Sprint-2/implement/querystring.test.js

@@ -10,3 +10,25 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+
+test("parses querystring with multiple values for the same key", () => {
+  expect(parseQueryString("name=John&name=Jane")).toEqual({
+    "name": "Jane",
+  });
+});
+
+test("parses querystring with empty values", () => {
+  expect(parseQueryString("name=&age=&city=")).toEqual({
+    "name": "",
+    "age": "",
+    "city": "",
+  });
+});
+
+test("parses querystring with only keys", () => {
+  expect(parseQueryString("name=&age&city")).toEqual({
+    "name": "",
+    "age": "",
+    "city": "",
+  });
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,14 @@
-function tally() {}
+function tally(items) {
+    if (!Array.isArray(items)) {
+      throw new Error("Input must be an array");
+    }
+
+    const counts = {};
+    for (const item of items) {
+      counts[item] = (counts[item] || 0) + 1;
+    }
+
+    return counts;
+  }
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -20,15 +20,42 @@ const tally = require("./tally.js");
 // When passed an array of items
 // Then it should return an object containing the count for each unique item
 
+test("tally returns counts for each unique item", () => {
+  const items = ['a', 'b', 'a', 'c', 'b', 'a'];
+  const expectedOutput = { a: 3, b: 2, c: 1 };
+  expect(tally(items)).toEqual(expectedOutput);
+});
 // 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 returns empty object for empty array", () => {
+  const items = [];
+  expect(tally(items)).toEqual({});
+});
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("tally returns counts for duplicate items", () => {
+  const items = ['x', 'y', 'x', 'z', 'y', 'x'];
+  const expectedOutput = { x: 3, y: 2, z: 1 };
+  expect(tally(items)).toEqual(expectedOutput);
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("tally throws error for invalid input", () => {
+  expect(() => tally("invalid")).toThrow("Input must be an array");
+});
+
+test("tally throws for number input", () => {
+    expect(() => tally(123)).toThrow("Input must be an array");
+  });
+
+  test("tally throws for object input", () => {
+    expect(() => tally({ a: 1 })).toThrow("Input must be an array");
+  });
+
+  test("tally throws for null input", () => {
+    expect(() => tally(null)).toThrow("Input must be an array");
+  });

Sprint-2/interpret/invert.js

@@ -16,14 +16,30 @@ function invert(obj) {
   return invertedObj;
 }
 
+
 // a) What is the current return value when invert is called with { a : 1 }
+// The current return value when invert is called with { a: 1 } is { key: 1 }.
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// The current return value when invert is called with { a: 1, b: 2 } is { key: 2 }.
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// The target return value when invert is called with { a: 1, b: 2 } should be { "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 the object.
+// It is needed in this program to iterate over the object's properties and their corresponding values.
 
 // d) Explain why the current return value is different from the target output
+// The current return value is different from the target output because the code incorrectly assigns the value to the key in the inverted object.
 
 // 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;
+}

Sprint-2/stretch/count-words.js

@@ -26,3 +26,51 @@
 
 3. Order the results to find out which word is the most common in the input
 */
+
+function countWords(str) {
+  // Split the string into words
+  const words = str.split(/\s+/);
+
+  // Create an object to hold the word counts
+  const wordCount = {};
+
+  // Loop through each word
+  for (const word of words) {
+    // Normalize the word to lowercase and remove punctuation
+    const cleanWord = word.toLowerCase().replace(/[.,!?]/g, '');
+
+    // If the word is not in the object, add it with a count of 1
+    if (!wordCount[cleanWord]) {
+      wordCount[cleanWord] = 1;
+    } else {
+      // If it exists, increment the count
+      wordCount[cleanWord]++;
+    }
+  }
+
+  return wordCount;
+}
+
+//function countWords(str) {
+//  const words = str.split(/\s+/);
+//  const counts = {};
+
+//  for (let word of words) {
+//    word = word.toLowerCase().replace(/[.,!?]/g, '');
+//    counts[word] = (counts[word] || 0) + 1;
+//  }
+
+//  return counts;
+// }
+
+// Example usage
+const result = countWords("you and me and you");
+console.log(result); // { you: 2, and: 2, me: 1 }   
+
+console.log(countWords("Hello, hello! How are you? You are great."));
+// { hello: 2, how: 1, are: 2, you: 2, great: 1 }
+console.log(countWords("This is a test. This test is only a test."));
+// { this: 2, is: 3, a: 2, test: 3, only: 1 }
+// Example with punctuation and case insensitivity
+console.log(countWords("Hello, world! Hello, everyone. Hello!"));
+// { hello: 3, world: 1, everyone: 1 }