London | 26-ITP-Jan | Alex Okorefe | sprint 2 | coursework

Sprint-2/debug/address.js

@@ -1,5 +1,9 @@
 // Predict and explain first...
 
+// The console.log statement is attempting to use an index [0] but const address is structured as an object not an array.
+// Since there is no property named 0 in the address object the console.log will return the string plus undefined.
+// We must use key value pairs to get the value. To locate items from an object we can either use dot notation or bracket notation.
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +16,4 @@ 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

@@ -3,6 +3,10 @@
 // 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
 
+// An object is not iterable by default it is a collection of keys and value pairs. This means their is no path for the for loop to follow.
+// Due to this when we run this code we are going to get a type error. To fix this and log all the property values in the object;
+// we must convert the object data into an array.
+
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +15,6 @@ 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 +4,18 @@
 // Each ingredient should be logged on a new line
 // How can you fix it?
 
+// I predict this code will log: bruschetta serves 2 followed by ingredients: and then [object Object]. It won't show the actual list of ingredients.
+// There are two main reasons this isn't working as intended:
+//      When you put ${recipe} inside a template literal, JavaScript doesn't know how to read the whole object into text, so it defaults to the placeholder [object Object]. We must point to the specific property, recipe.ingredients, instead.
+//      In addition to this; even if you point to recipe.ingredients, it's an array. If we want each ingredient to appear on a new line to meet the requirements, we will need to use the .join("\n") method. The \n acts as a newline character.
+
 const recipe = {
   title: "bruschetta",
   serves: 2,
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
+const formattedIngredients = recipe.ingredients.join("\n");
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${formattedIngredients}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,11 @@
-function contains() {}
+function contains(obj, propertyName) {
+  // 1. Check if 'obj' is a valid object and NOT an array
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+  }
+
+  // 2. Check if the propertyName exists as a key in the object
+  return propertyName in obj;
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,16 +20,44 @@ 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("returns false when empty object", () => {
+  const input = {};
+  const result = contains(input, "a");
+  expect(result).toBe(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
 
+test("returns true when the property exists in the object", () => {
+  const input = { firstName: "Alex", age: 30 };
+  const result = contains(input, "firstName");
+  expect(result).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 when the property does not exist in the object", () => {
+  const input = { firstName: "Alex", age: 30 };
+  const result = contains(input, "lastName");
+  expect(result).toBe(false);
+});
+
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+
+test("returns false when the input is an array instead of an object", () => {
+  const input = [1, 2, 3];
+  const result = contains(input, "0"); // Even though index 0 exists, it's an array
+  expect(result).toBe(false);
+});
+
+// 5. Given null or other types
+test("returns false when the input is null or undefined", () => {
+  expect(contains(null, "prop")).toBe(false);
+  expect(contains(undefined, "prop")).toBe(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,14 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  const lookup = {};
+
+  for (const pair of countryCurrencyPairs) {
+    const country = pair[0];
+    const currency = pair[1];
+
+    lookup[country] = currency;
+  }
+
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/querystring.js

@@ -1,13 +1,44 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
+  if (typeof queryString !== "string") {
     return queryParams;
   }
+
+  if (queryString.startsWith("?")) {
+    queryString = queryString.substring(1);
+  }
+
+  if (queryString.trim() === "") {
+    return queryParams;
+  }
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (!pair) continue;
+
+    const equalIndex = pair.indexOf("=");
+
+    let key = pair;
+    let value = "";
+
+    if (equalIndex !== -1) {
+      key = pair.substring(0, equalIndex);
+      value = pair.substring(equalIndex + 1);
+    }
+
+    key = decodeURIComponent(key);
+    value = decodeURIComponent(value);
+
+    if (queryParams.hasOwnProperty(key)) {
+      if (Array.isArray(queryParams[key])) {
+        queryParams[key].push(value);
+      } else {
+        queryParams[key] = [queryParams[key], value];
+      }
+    } else {
+      queryParams[key] = value;
+    }
   }
 
   return queryParams;

Sprint-2/implement/querystring.test.js

@@ -3,10 +3,52 @@
 // 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 querystring values missing = sign", () => {
+  expect(parseQueryString("userId=101&username=jdoe&isActive")).toEqual({
+    userId: "101",
+    username: "Aokorefe",
+    isActive: "",
+  });
+});
+
+test("parses querystring values containing no key and value but only =", () => {
+  expect(parseQueryString("=&priority=high&taskId=42&=&=")).toEqual({
+    priority: "high",
+    taskId: "42",
+  });
+});
+
+test("parses querystring with encoded keys and values", () => {
+  expect(
+    parseQueryString(
+      "query=web%20design&location=San%20Francisco&query=ui%20ux"
+    )
+  ).toEqual({
+    query: ["web design", "ui ux"],
+    location: "London",
+  });
+});
+
+test("parses querystring values containing repetitive keys", () => {
+  expect(
+    parseQueryString("tag=frontend&count=10&tag=backend&tag=devops&count=20")
+  ).toEqual({
+    tag: ["frontend", "backend", "devops"],
+    count: ["10", "20"],
+  });
+});
+
+test("parses querystring with leading ?", () => {
+  expect(parseQueryString("?search=javascript&sort=asc")).toEqual({
+    search: "javascript",
+    sort: "asc",
   });
 });

Sprint-2/implement/tally.js

@@ -1,3 +1,17 @@
-function tally() {}
+function tally(items) {
+  // Check for valid input
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  const counts = {};
+
+  for (const item of items) {
+    // If the item exists, increment; otherwise, initialize to 1
+    counts[item] = (counts[item] || 0) + 1;
+  }
+
+  return counts;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,12 +23,18 @@ 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 on an array with duplicate items returns correct counts", () =>
+  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 an error when passed a string", () => {
+  expect(() => tally("not an array")).toThrow();
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,34 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
 // 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 }
 
+// { 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?
 
+// Object.entries returns an array of a given object's own enumerable string-keyed property [key, value] pairs.
+// It is needed in this program to iterate over the key-value pairs of the input object and swap them to create the inverted object.
+
 // 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 is assigning
+// the value to a property named "key" in the invertedObj, instead of using the actual key from the input object.
+// This results in only the last key-value pair being stored in the invertedObj, and it does not correctly swap the keys and values as intended.
+
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+module.exports = invert;

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,22 @@
+const invert = require("./invert");
+
+describe("invert()", () => {
+  test("inverts a single key-value pair", () => {
+    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("handles an empty object", () => {
+    expect(invert({})).toEqual({});
+  });
+
+  test("inverts an object with string values", () => {
+    expect(invert({ first: "John", last: "Doe" })).toEqual({
+      Alex: "first",
+      Doe: "last",
+    });
+  });
+});