Barcelona | OCT25 | Tatiana Kuzmina | Sprint 2 | Module-Data-Groups

Sprint-2/debug/address.js

@@ -12,4 +12,4 @@ 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

@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -11,5 +11,5 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:
+${recipe.ingredients.join("\n")}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,7 @@
-function contains() {}
+function contains(obj, propertyName) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+  }
 
-module.exports = contains;
+  return Object.hasOwn(obj, propertyName);
+}

Sprint-2/implement/lookup.js

@@ -1,5 +1,12 @@
-function createLookup() {
-  // implementation here
-}
+function createLookup(countryCurrencyPairs) {
+  const lookup = {};
+
+  for (const pair of countryCurrencyPairs) {
+    const countryCode = pair[0];
+    const currencyCode = pair[1];
 
-module.exports = createLookup;
+    lookup[countryCode] = currencyCode;
+  }
+
+  return lookup;
+}

Sprint-2/implement/querystring.js

@@ -1,13 +1,21 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
+  if (!queryString || queryString.length === 0) {
     return queryParams;
   }
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    const firstEqualsIndex = pair.indexOf("=");
+
+    if (firstEqualsIndex !== -1) {
+      const key = pair.slice(0, firstEqualsIndex);
+      const value = pair.slice(firstEqualsIndex + 1);
+      queryParams[key] = value;
+    } else {
+      queryParams[pair] = "";
+    }
   }
 
   return queryParams;

Sprint-2/implement/tally.js

@@ -1,3 +1,19 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  const result = {};
+
+  for (const item of items) {
+    if (result[item]) {
+      result[item] += 1;
+    } else {
+      result[item] = 1;
+    }
+  }
+
+  return result;
+}
 
 module.exports = tally;

Sprint-2/interpret/invert.js

@@ -10,20 +10,33 @@ 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 }
+module.exports = invert;
 
+// a) What is the current return value when invert is called with { a : 1 }
+// Current return value for { a : 1 } { key: "a" }
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
-
+// Current return value for { a: 1, b: 2 } { key: "b" } (The second iteration overwrites the first).
 // c) What is the target return value when invert is called with {a : 1, b: 2}
-
+// Target return value for { a: 1, b: 2 } { "1": "a", "2": "b" }
 // c) What does Object.entries return? Why is it needed in this program?
-
+// t returns an array of [key, value] pairs (e.g., [["a", 1]]). It is needed to easily iterate over both keys and values using a for...of loop.
 // d) Explain why the current return value is different from the target output
-
+// The code uses dot notation (.key), which creates a literal property named "key". To use the content of a variable as a property name, you must use bracket notation ([value]).
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+test("inverts a simple object", () => {
+  expect(invert({ x: 10, y: 20 })).toEqual({ 10: "x", 20: "y" });
+});
+
+test("inverts an object with multiple properties", () => {
+  expect(invert({ a: 1, b: 2, c: 3 })).toEqual({ 1: "a", 2: "b", 3: "c" });
+});
+
+test("returns empty object when passed empty object", () => {
+  expect(invert({})).toEqual({});
+});