London | 25-ITP-May | Houssam Lahlah | Sprint 2 | Sprint-2

Sprint-2/debug/address.js

@@ -1,4 +1,6 @@
-// Predict and explain first...
+// The original code used address[0], which doesn't work because
+// address is an object, not an array. Objects have named keys, not numeric indexes.
+// So address[0] is undefined.
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +14,4 @@ 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

@@ -1,7 +1,7 @@
-// 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
+// Prediction and explanation:
+// The original code uses `for (const value of author)`, but `author` is an object,
+// not an array or other iterable. This will throw a TypeError.
+// To fix it, we need to loop over the object's values using Object.values().
 
 const author = {
   firstName: "Zadie",
@@ -11,6 +11,8 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+// Fix: use Object.values() to get an array of the values
+for (const value of Object.values(author)) {
   console.log(value);
 }
+

Sprint-2/debug/recipe.js

@@ -1,15 +1,19 @@
-// Predict and explain first...
-
-// 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?
+// Prediction and explanation:
+// The current code tries to log the whole `recipe` object with `${recipe}`,
+// but objects are not automatically formatted in a readable way in a template string.
+// This will print something like "[object Object]" instead of the ingredients on separate lines.
+// To fix it, we need to access the `ingredients` array and log each ingredient individually.
 
 const recipe = {
   title: "bruschetta",
   serves: 2,
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
+// Fix: log title and serves, then loop over ingredients to print each on a new line
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:`);
+for (const ingredient of recipe.ingredients) {
+  console.log(ingredient);
+}
+

Sprint-2/implement/contains.js

@@ -1,3 +1,12 @@
-function contains() {}
+function contains(obj, prop) {
+  // Check if the input is a valid object and prop is a string
+  if (obj === null || typeof obj !== "object" || Array.isArray(obj)) {
+    return false;
+  }
+
+  // Use Object.hasOwn to check if property exists
+  return Object.hasOwn(obj, prop);
+}
 
 module.exports = contains;
+

Sprint-2/implement/contains.test.js

@@ -1,35 +1,31 @@
 const contains = require("./contains.js");
 
-/*
-Implement a function called contains that checks an object contains a
-particular property
-
-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'
-*/
-
-// Acceptance criteria:
-
-// 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
-
 // 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 returns true when object has the property", () => {
+  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 returns false when object does not have the property", () => {
+  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
+// Then it should return false
+test("contains returns false for invalid input like arrays", () => {
+  expect(contains([], "a")).toBe(false);
+  expect(contains(null, "a")).toBe(false);
+});
+

Sprint-2/implement/lookup.js

@@ -1,5 +1,15 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  // Validate input: must be an array of arrays
+  if (!Array.isArray(pairs)) {
+    return {};
+  }
+
+  const lookup = {};
+  for (const [country, currency] of pairs) {
+    lookup[country] = currency;
+  }
+  return lookup;
 }
 
 module.exports = createLookup;
+

Sprint-2/implement/lookup.test.js

@@ -1,35 +1,26 @@
 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 input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+    ["GB", "GBP"],
+  ];
+  const result = createLookup(input);
+
+  expect(result).toEqual({
+    US: "USD",
+    CA: "CAD",
+    GB: "GBP",
+  });
+});
+
+test("returns empty object when given an empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+test("returns empty object when given invalid input", () => {
+  expect(createLookup(null)).toEqual({});
+  expect(createLookup("not an array")).toEqual({});
+});
 
-/*
-
-Create a lookup object of key value pairs from an array of code pairs
-
-Acceptance Criteria:
-
-Given
- - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
-
-When
- - createLookup function is called with the country-currency array as an argument
-
-Then
- - It should return an object where:
- - The keys are the country codes
- - The values are the corresponding currency codes
-
-Example
-Given: [['US', 'USD'], ['CA', 'CAD']]
-
-When
-createLookup(countryCurrencyPairs) is called
-
-Then
-It should return:
- {
-   'US': 'USD',
-   'CA': 'CAD'
- }
-*/

Sprint-2/implement/querystring.js

@@ -1,16 +1,60 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
+
+  // Guard: empty or falsy input
+  if (!queryString) return queryParams;
+
+  // Remove leading '?'
+  if (queryString.startsWith("?")) {
+    queryString = queryString.slice(1);
+    if (queryString.length === 0) return queryParams;
   }
-  const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+  const pairs = queryString.split("&").filter((p) => p.length > 0);
+
+  const safeDecode = (s) => {
+    // Replace + with space before decoding
+    const replaced = s.replace(/\+/g, " ");
+    try {
+      return decodeURIComponent(replaced);
+    } catch (e) {
+      // If decoding fails, return the replaced string as-is
+      return replaced;
+    }
+  };
+
+  for (const pair of pairs) {
+    const idx = pair.indexOf("=");
+
+    let key;
+    let value;
+    if (idx === -1) {
+      // No '=' present: treat as key with empty string value
+      key = pair;
+      value = "";
+    } else {
+      // Split on first '=' only
+      key = pair.slice(0, idx);
+      value = pair.slice(idx + 1);
+    }
+
+    const decodedKey = safeDecode(key);
+    const decodedValue = safeDecode(value);
+
+    if (Object.prototype.hasOwnProperty.call(queryParams, decodedKey)) {
+      const existing = queryParams[decodedKey];
+      if (Array.isArray(existing)) {
+        existing.push(decodedValue);
+      } else {
+        queryParams[decodedKey] = [existing, decodedValue];
+      }
+    } else {
+      queryParams[decodedKey] = decodedValue;
+    }
   }
 
   return queryParams;
 }
 
 module.exports = parseQueryString;
+

Sprint-2/implement/querystring.test.js

@@ -1,12 +1,33 @@
-// In the prep, we implemented a function to parse query strings.
-// Unfortunately, it contains several bugs!
-// 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",
+    equation: "x=y+1",
   });
 });
+
+test("parses basic key/value pairs", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({ a: "1", b: "2" });
+});
+
+test("handles empty query string", () => {
+  expect(parseQueryString("")).toEqual({});
+  expect(parseQueryString("?")).toEqual({});
+});
+
+test("handles keys without value and keys with empty value", () => {
+  expect(parseQueryString("noValue")).toEqual({ noValue: "" });
+  expect(parseQueryString("empty=")).toEqual({ empty: "" });
+});
+
+test("decodes percent-encoding and plus signs", () => {
+  expect(parseQueryString("name=John%20Doe&query=hello+world")).toEqual({
+    name: "John Doe",
+    query: "hello world",
+  });
+});
+
+test("collects duplicate keys into arrays in order", () => {
+  expect(parseQueryString("a=1&a=2&a=3")).toEqual({ a: ["1", "2", "3"] });
+});
+

Sprint-2/implement/tally.js

@@ -1,3 +1,18 @@
-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] ++;
+    } else {
+      result[item] = 1;
+    }
+  }
+  return result;
+}
 
 module.exports = tally;
+

Sprint-2/implement/tally.test.js

@@ -1,34 +1,27 @@
 const tally = require("./tally.js");
 
-/**
- * tally array
- *
- * In this task, you'll need to implement a function called tally
- * that will take a list of items and count the frequency of each item
- * in an array
- *
- * For example:
- *
- * tally(['a']), target output: { a: 1 }
- * tally(['a', 'a', 'a']), target output: { a: 3 }
- * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
- */
-
-// Acceptance criteria:
-
-// Given a function called tally
-// When passed an array of items
-// Then it should return an object containing the count for each unique item
-
 // 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 counts items correctly", () => {
+  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 for invalid input", () => {
+  expect(() => tally("not an array")).toThrow("Input must be an array");
+  expect(() => tally(null)).toThrow("Input must be an array");
+  expect(() => tally(123)).toThrow("Input must be an array");
+});
+