London | 26-ITP-May | Vito Moratti | Sprint 2 | Coursework

Sprint-2/debug/address.js

@@ -12,4 +12,7 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address["houseNumber"]}`);
+// to access the houseNumber of the object using bracket notation,
+//  we need to use the key as a string. In this case, "houseNumber"
+//  is the correct key, so the code should work as expected.

Sprint-2/debug/author.js

@@ -3,13 +3,18 @@
 // 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
 
-const author = {
-  firstName: "Zadie",
-  lastName: "Smith",
-  occupation: "writer",
-  age: 40,
-  alive: true,
-};
+// I think the issue with the original code is it was trying to loop over the object directly,
+//  which is not iterable. Instead, we should loop over the array that contains the object.
+
+const author = [
+  {
+    firstName: "Zadie",
+    lastName: "Smith",
+    occupation: "writer",
+    age: 40,
+    alive: true,
+  },
+];
 
 for (const value of author) {
   console.log(value);

Sprint-2/debug/recipe.js

@@ -12,4 +12,5 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`); //the DOT expression was missing in the original code.
+// also adding a join method to the ingredients array to log each ingredient on a new line.

Sprint-2/implement/contains.js

@@ -1,3 +1,5 @@
-function contains() {}
+function contains(obj, prop) {
+  return prop in obj; // checks if the property exists in the object and returns true or false
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -17,19 +17,31 @@ 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");
+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 an object returns true, or false otherwise", () => {
+  expect(contains({a: 1, b: 2, c: 3}, "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 an object returns true, or false otherwise", () => {
+  expect(contains({a: 1, b: 2, c: 3}, "d")).toBe(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("contains an object returns true, or false otherwise", () => {
+  expect(contains([1, 2, 3, 'a'], "a")).toBe(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,6 @@
-function createLookup() {
-  // implementation here
+function createLookup(entries) {
+    let obj = Object.fromEntries(entries);
+    return obj;
 }
 
-module.exports = createLookup;
+module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,11 @@
 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", () => {
+  expect(createLookup([['US', 'USD'], ['CA', 'CAD']])).toEqual({
+    'US': 'USD',
+    'CA': 'CAD'
+  });
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -3,11 +3,31 @@ function parseQueryString(queryString) {
   if (queryString.length === 0) {
     return queryParams;
   }
+  queryString = queryString.replace(/\+/g, " ");
   const keyValuePairs = queryString.split("&");
-
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (pair === "") {
+      continue;
+    }
+    let key;
+    let value;
+    const index = pair.indexOf("=");
+    if (index === -1) {
+      key = decodeURIComponent(pair);
+      value = "";
+    } else {
+      key = decodeURIComponent(pair.slice(0, index));
+      value = decodeURIComponent(pair.slice(index + 1));
+    }
+    if (!queryParams[key]) {
+      queryParams[key] = value;
+    } else {
+      if (Array.isArray(queryParams[key])) {
+        queryParams[key].push(value);
+      } else {
+        queryParams[key] = [queryParams[key], value];
+      }
+    }
   }
 
   return queryParams;

Sprint-2/implement/tally.js

@@ -1,3 +1,20 @@
-function tally() {}
+function tally(arr) {
+  let countOfItemsObj = {};
+  if (!Array.isArray(arr)) {
+    throw new Error("Invalid input");
+  } else if (arr.length < 1) {
+    return countOfItemsObj;
+  } else {
+    for (let element = 0; element < arr.length; element++) {
+      const exist = Object.hasOwn(countOfItemsObj, arr[element]);
+      if (!exist) {
+        countOfItemsObj[arr[element]] = 1;
+      } else {
+        countOfItemsObj[arr[element]] = countOfItemsObj[arr[element]] + 1;
+      }
+    }
+  }
+  return countOfItemsObj;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,12 +23,20 @@ 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 counts for each unique item", () => {
+  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 on an invalid input like a string throws an error", () => {
+  expect(() => tally("invalid input")).toThrow("Invalid input");
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,40 @@ 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 }
+// the current return value is { key: 1 }
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// current return value is { key: 2 }
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// the target return value is { "1": "a", "2": "b" }
 
 // c) What does Object.entries return? Why is it needed in this program?
+// Object.entries returns an array of key-value pairs from the object. It is needed 
+// in this program to iterate over each key-value pair in the object so that we can
+// swap them and create a new inverted object.
 
 // d) Explain why the current return value is different from the target output
+// I think current return value is different from the return value because the
+//  current implementation is not really swapping the properties of the object.
+//  Instead, it is just creating a new property called "key" and assigning the 
+// value to it. The target output requires us to swap the keys and values, which
+//  is not happening in the current implementation.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+console.assert(
+  JSON.stringify(invert({ a: 1 })) === JSON.stringify({ "1": "a" }),
+  "Test 1 failed"
+);
+
+console.assert(
+  JSON.stringify(invert({ a: 1, b: 2 })) ===
+    JSON.stringify({ "1": "a", "2": "b" }),
+  "Test 2 failed"
+);