Cape Town | 2026-ITP-Jan | Isaac Abodunrin | Sprint 2 | Grouping data: Objects

Sprint-2/debug/address.js

@@ -1,9 +1,3 @@
-// Predict and explain first...
-
-// This code should log out the houseNumber from the address object
-// but it isn't working...
-// Fix anything that isn't working
-
 const address = {
   houseNumber: 42,
   street: "Imaginary Road",
@@ -12,4 +6,9 @@ const address = {
   postcode: "XYZ 123",
 };
 
+/* Prediction */
+// This will throw an error. This is because unlike lists, key values are selected using a '.'
 console.log(`My house number is ${address[0]}`);
+
+/* Fix */
+console.log(`My house number is ${address.houseNumber}`);

Sprint-2/debug/author.js

@@ -1,8 +1,4 @@
-// Predict and explain first...
-
-// 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
-
+/* ======== Initial Script ======= */
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +7,25 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+try {
+  for (const value of author) {
+    console.log(value);
+  }
+} catch (error) {
+  console.error("Error:", error.message);
+}
+
+/* ============== Prediction ============== */
+// It will print out only the name of the keys (i.e. firstName, lastName,
+// occupation, age, and alive), but not their actual values.
+
+/* ============== Actual Result ============== */
+// Error: author is not iterable.
+// This error occurs because the for...of loop can only be used with
+// iterable objects like arrays, strings, etc. Since 'author' is an object,
+// it is not iterable. To fix this, we can use a for...in loop instead.
+
+/* ============== Corrected Script ============== */
+for (const key in author) {
+  console.log(author[key]);
 }

Sprint-2/debug/recipe.js

@@ -4,6 +4,7 @@
 // Each ingredient should be logged on a new line
 // How can you fix it?
 
+/* ============== Initial Script ============== */
 const recipe = {
   title: "bruschetta",
   serves: 2,
@@ -13,3 +14,18 @@ const recipe = {
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
 ${recipe}`);
+
+/* ============== Prediction ============== */
+// It will throw an error when trying to print the ingredients.
+// This is because the entire recipe object was called instead of
+// just its ingredients property. JavaScript cannot print an object,
+// hence the error is thrown.
+
+/// ============== Actual Result ============== */
+// It tunrs out that JavaScript does not throw an error when
+// trying to print an object. Instead, it prints out [object Object].
+
+/* ============== Corrected Script ============== */
+console.log(`${recipe.title} serves ${recipe.serves}
+  ingredients:
+    - ${recipe.ingredients.join("\n    - ")}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,11 @@
-function contains() {}
+function contains(object, property) {
+  if (typeof object !== "object" || object === null || Array.isArray(object)) {
+    throw new TypeError(
+      "First argument must be an object in the form { key: value }"
+    );
+  }
+
+  return object.hasOwnProperty(property);
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -1,35 +1,78 @@
 const contains = require("./contains.js");
 
-/*
-Implement a function called contains that checks an object contains a
-particular property
+describe("contains", () => {
+  // Case 1: Should return true if the property exists in object.
+  test("should return true when object contains passed property name", () => {
+    const objsWithValidProps = [
+      [{ a: 1, b: 2 }, "b"],
+      [{ name: "John", age: 30 }, "name"],
+      [{ nested: { key: "value" } }, "nested"],
+      [{ id: 123, status: "active", language: "JavaScript" }, "status"],
+      [{ data: [], items: null }, "data"],
+    ];
 
-E.g. contains({a: 1, b: 2}, 'a') // returns true
-as the object contains a key of 'a'
+    objsWithValidProps.forEach(([obj, prop]) => {
+      expect(contains(obj, prop)).toEqual(true);
+    });
+  });
 
-E.g. contains({a: 1, b: 2}, 'c') // returns false
-as the object doesn't contains a key of 'c'
-*/
+  // Case 2: Should return false if the object does not contain the given property.
+  test("should return false when object does not contain passed property name", () => {
+    const objsWithoutProps = [
+      [{ a: 1, b: 2 }, "c"],
+      [{ name: "John", age: 30 }, "email"],
+      [{ nested: { key: "value" } }, "nonexistent"],
+      [{ id: 123, status: "active", language: "JavaScript" }, "description"],
+      [{ data: [], items: null }, "nonexistent"],
+    ];
 
-// Acceptance criteria:
+    objsWithoutProps.forEach(([obj, prop]) => {
+      expect(contains(obj, prop)).toEqual(false);
+    });
+  });
 
-// 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
+  // Case 3: Should return false if the object is empty.
+  test("should return false when object is empty", () => {
+    expect(contains({}, "anyProperty")).toEqual(false);
+  });
 
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
+  // Case 4: Should return false for properties that only exist in the prototype chain
+  test("should return false for properties in prototype chain", () => {
+    const objsWithProtoProps = [
+      [{ a: 1 }, "toString"],
+      [{ name: "John", age: 30 }, "hasOwnProperty"],
+      [{ nested: { key: "value" } }, "isPrototypeOf"],
+    ];
 
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
+    objsWithProtoProps.forEach(([obj, prop]) => {
+      expect(contains(obj, prop)).toEqual(false);
+    });
+  });
 
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
+  // Case 5: Should throw an error if an array is passed
+  test("should throw error when array is passed", () => {
+    expect(() => contains(["string"], 0)).toThrow(
+      "First argument must be an object in the form { key: value }"
+    );
+  });
 
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+  // Case 6: Should throw an error if a non-object is passed
+  test("should throw error when non-object is passed", () => {
+    const nonObjects = [
+      null,
+      undefined,
+      42,
+      "The Curse",
+      true,
+      Infinity,
+      Symbol("sym"),
+      function () {},
+    ];
+
+    nonObjects.forEach((nonObj) => {
+      expect(() => contains(nonObj, "prop")).toThrow(
+        "First argument must be an object in the form { key: value }"
+      );
+    });
+  });
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,35 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  let countryCurrencyObj = {};
+
+  for (const countryCurrencyPair of countryCurrencyPairs) {
+    if (!Array.isArray(countryCurrencyPair)) {
+      throw new Error("Country-currency pairs must be in array format");
+    }
+
+    if (countryCurrencyPair.length !== 2) {
+      throw new Error(
+        "Country-currency pairs must contain exactly two elements: country and currency"
+      );
+    }
+
+    let [country, currency] = countryCurrencyPair;
+
+    if (typeof country !== "string" || typeof currency !== "string") {
+      throw new Error("Country-currency pairs must be in string format");
+    }
+
+    if (country.trim() === "" || currency.trim() === "") {
+      throw new Error("Country and currency codes cannot be empty");
+    }
+
+    if (countryCurrencyObj[country]) {
+      throw new Error(`Duplicate country code found: ${country}`);
+    }
+
+    countryCurrencyObj[country] = currency;
+  }
+
+  return countryCurrencyObj;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,35 +1,112 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+describe("createLookup", () => {
+  // Case 1: Returns an empty object if no country-currency pairs are provided
+  test("returns an empty object if no country-currency pairs are provided", () => {
+    const countryCurrencyPairs = [];
+    const currencyObj = createLookup(countryCurrencyPairs);
 
-/*
+    expect(currencyObj).toEqual({});
+  });
 
-Create a lookup object of key value pairs from an array of code pairs
+  // Case 2: Returns country currency code lookup for a single country-currency pair
+  test("creates a country currency code lookup for a single code pair", () => {
+    const countryCurrencyPairs = [["US", "USD"]];
+    const currencyObj = createLookup(countryCurrencyPairs);
 
-Acceptance Criteria:
+    expect(currencyObj).toEqual({
+      US: "USD",
+    });
+  });
 
-Given
- - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
+  // Case 3: Returns country currency codes lookup for multiple country-currency pairs
+  test("creates a country currency code lookup for multiple codes", () => {
+    const countryCurrencyPairs = [
+      ["US", "USD"],
+      ["CA", "CAD"],
+      ["GB", "GBP"],
+      ["ZA", "ZAR"],
+      ["NG", "NGN"],
+    ];
 
-When
- - createLookup function is called with the country-currency array as an argument
+    const inputCurrencyPairObj = createLookup(countryCurrencyPairs);
+    const outputCurrencyPairObj = {
+      US: "USD",
+      CA: "CAD",
+      GB: "GBP",
+      ZA: "ZAR",
+      NG: "NGN",
+    };
 
-Then
- - It should return an object where:
- - The keys are the country codes
- - The values are the corresponding currency codes
+    expect(inputCurrencyPairObj).toEqual(outputCurrencyPairObj);
+  });
 
-Example
-Given: [['US', 'USD'], ['CA', 'CAD']]
+  // Case 4: Throws an error if a country-currency pair is not an array
+  test("throws an error if a country-currency pair is not an array", () => {
+    const countryCurrencyPairs = [
+      ["US", "USD"],
+      ["CA", "CAD"],
+      "GB-GBP",
+      ["ZA", "ZAR"],
+      ["NG", "NGN"],
+    ];
 
-When
-createLookup(countryCurrencyPairs) is called
+    expect(() => createLookup(countryCurrencyPairs)).toThrow(
+      "Country-currency pairs must be in array format"
+    );
+  });
 
-Then
-It should return:
- {
-   'US': 'USD',
-   'CA': 'CAD'
- }
-*/
+  // Case 5: Throws an error if a country-currency pair is missing a country or currency
+  test("throws an error if a country-currency pair is missing a country or currency", () => {
+    const countryCurrencyPairs = [
+      ["US", ""],
+      ["", "CAD"],
+      ["  ", "GBP"],
+    ];
+
+    for (const currencyPair of countryCurrencyPairs) {
+      expect(() => createLookup([currencyPair])).toThrow(
+        "Country and currency codes cannot be empty"
+      );
+    }
+  });
+
+  // Case 6: Throws an error if a country-currency pair contains more than two elements
+  test("throws an error if a country-currency pair contains more than two elements", () => {
+    const countryCurrencyPairs = [["GB", "GBP", "ZAR"]];
+
+    expect(() => createLookup(countryCurrencyPairs)).toThrow(
+      "Country-currency pairs must contain exactly two elements: country and currency"
+    );
+  });
+
+  // Case 7: Throws and error if a country-currency pair is duplicated
+  test("throws an error if a country-currency pair is duplicated", () => {
+    const countryCurrencyPairs = [
+      ["US", "USD"],
+      ["CA", "CAD"],
+      ["US", "USD"],
+    ];
+
+    expect(() => createLookup(countryCurrencyPairs)).toThrow(
+      "Duplicate country code found: US"
+    );
+  });
+
+  // Case 8: Throws an error if non-string values are used as country or currency codes
+  test("throws an error if non-string values are used as country or currency codes", () => {
+    const countryCurrencyPairs = [
+      [{ name: "United States" }, "USD"],
+      ["CA", Infinity],
+      ["GB", 1.21],
+      [undefined, "ZAR"],
+      ["NG", null],
+    ];
+
+    for (const currencyPair of countryCurrencyPairs) {
+      expect(() => createLookup([currencyPair])).toThrow(
+        "Country-currency pairs must be in string format"
+      );
+    }
+  });
+});