Glasgow | ITP MAY | MIRABELLE MORAH | Module Data Groups | Sprint-2

Sprint-2/debug/address.js

@@ -1,5 +1,7 @@
 // Predict and explain first...
 
+// It returns back "My house number is undefined" because it's accessing properties using an index instead of the property name.
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +14,6 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+//added dot notation to access houseNumber
+
+console.log(`My house number is ${address.houseNumber}`);

Sprint-2/debug/author.js

@@ -1,8 +1,13 @@
 // Predict and explain first...
 
+// no proper use of for 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
 
+// error in line 16 and throws the error "TypeError: author is not iterable at Object." So this does not work on objects.
+
+
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +16,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -4,12 +4,13 @@
 // Each ingredient should be logged on a new line
 // How can you fix it?
 
+// no access to recipe object properties causes problems. Hence we need to use the correct syntax to access the properties.
+
 const recipe = {
   title: "bruschetta",
   serves: 2,
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients: ${recipe.ingredients.join("\n")}`);

Sprint-2/implement/contains.js

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

Sprint-2/implement/contains.test.js

@@ -17,19 +17,39 @@ as the object doesn't contains a key of 'c'
 // When passed an object and a property name
 // Then it should return true if the object contains the property, false otherwise
 
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+describe("contains function", () => {
+
+  // Given an empty object
+  // When passed to contains
+  // Then it should return false
+
+  test("contains on empty object returns false", () => {
+    expect(contains({}, "any")).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", () => {
+    expect(contains({a: 1, b: 2}, "a")).toBe(true);
+    expect(contains({x: 10, y: 20}, "y")).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", () => {
+    expect(contains({a: 1, b: 2}, "c")).toBe(false);
+    expect(contains({x: 10, y: 20}, "z")).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 arrays or non-object", () => {
+    expect(contains([], "length")).toBe(false);
+    expect(contains(null, "a")).toBe(false);
+    expect(contains(undefined, "a")).toBe(false);
+    expect(contains(42, "a")).toBe(false);
+  });
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,17 @@
-function createLookup() {
-  // implementation here
+function createLookup(codePairs) {
+
+  const lookup = {}; // Initialize an empty object to store the lookup pairs
+
+  // Iterate over each pair in the input array
+  for (const pair of codePairs) {
+    // Ensure the pair has at least two elements (key and value)
+    if (pair && pair.length >= 2) {
+      const key = pair[0];   // The first element is the key (e.g., 'US')
+      const value = pair[1]; // The second element is the value (e.g., 'USD')
+      lookup[key] = value;   // Assign the value to the key in the lookup object
+    }
+}
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,44 @@
 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"],
+    ["GB", "GBP"],
+    ["JP", "JPY"],
+  ];
+
+  const expectedLookup = {
+    US: "USD",
+    CA: "CAD",
+    GB: "GBP",
+    JP: "JPY",
+  };
+
+  const result = createLookup(countryCurrencyPairs);
+
+  expect(result).toEqual(expectedLookup);
+});
+
+test("handles an empty array", () => {
+  const countryCurrencyPairs = [];
+  const expectedLookup = {};
+  const result = createLookup(countryCurrencyPairs);
+  expect(result).toEqual(expectedLookup);
+});
+
+test("handles pairs with missing values (should still set key with undefined/null)", () => {
+  const countryCurrencyPairs = [
+    ["DE", "EUR"],
+    ["XX"], // Missing currency code
+  ];
+  const expectedLookup = {
+    DE: "EUR",
+    XX: undefined,
+  };
+  const result = createLookup(countryCurrencyPairs);
+  expect(result).toEqual(expectedLookup);
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -1,13 +1,12 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
-  }
-  const keyValuePairs = queryString.split("&");
+  if (!queryString) return queryParams;
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+  for (const pair of queryString.split("&")) {
+    if (!pair) continue;
+    const [key, ...rest] = pair.split("=");
+    const value = rest.length > 0 ? rest.join("=") : "";
+    queryParams[decodeURIComponent(key)] = decodeURIComponent(value);
   }
 
   return queryParams;

Sprint-2/implement/querystring.test.js

@@ -10,3 +10,26 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+
+test("parses multiple key-value pairs", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({ a: "1", b: "2" });
+});
+
+test("parses keys with empty values", () => {
+  expect(parseQueryString("a=&b=2")).toEqual({ a: "", b: "2" });
+});
+
+test("parses keys with no value", () => {
+  expect(parseQueryString("a&b=2")).toEqual({ a: "", b: "2" });
+});
+
+test("parses empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses encoded characters", () => {
+  expect(parseQueryString("name=John%20Doe&city=New%20York")).toEqual({
+    name: "John Doe",
+    city: "New York",
+  });
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,12 @@
-function tally() {}
+function tally(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("Input must be an array");
+  }
+  const counts = {};
+  for (const item of list) {
+    counts[item] = (counts[item] || 0) + 1;
+  }
+  return counts;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,12 +23,24 @@ 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");
+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 returns counts for each unique item", () => {
+  expect(tally(["a"])).toEqual({ a: 1 });
+  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 error on invalid input", () => {
+  expect(() => tally("not an array")).toThrow("Input must be an array");
+  expect(() => tally(123)).toThrow("Input must be an array");
+  expect(() => tally({})).toThrow("Input must be an array");
+});

Sprint-2/interpret/invert.js

@@ -6,6 +6,7 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
+/*
 function invert(obj) {
   const invertedObj = {};
 
@@ -16,14 +17,43 @@ function invert(obj) {
   return invertedObj;
 }
 
+console.log(invert({ a: 1, b: 2 }));
+
+*/
+
 // a) What is the current return value when invert is called with { a : 1 }
 
+// ... currently gives { key: 1 } 
+
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
 
+// ... currently gives { key: 2 }
+
 // c) What is 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?
 
-// d) Explain why the current return value is different from the target output
+// ... Object.entries returns an array of key-value pairs from the object, which allows us to iterate over them easily.
+
+// d) Explain why the current return value is different from the target output 
+
+// ... The current implementation incorrectly assigns the value to the key property of invertedObj instead of using the value as a key in invertedObj. fixed by using invertedObj[value] = key;
 
 // 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(invert({ a: 1 }));
+console.log(invert({ a: 1, b: 2 }));
+
+module.exports = invert;

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,18 @@
+const invert = require("./invert.js");
+
+test("invert swaps keys and values for single pair", () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+test("invert swaps keys and values for multiple pairs", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ "1": "a", "2": "b" });
+  expect(invert({ x: 10, y: 20 })).toEqual({ "10": "x", "20": "y" });
+});
+
+test("invert works with string values", () => {
+  expect(invert({ a: "apple", b: "banana" })).toEqual({ apple: "a", banana: "b" });
+});
+
+test("invert returns empty object for empty input", () => {
+  expect(invert({})).toEqual({});
+});