Glasgow | 26-ITP-May | Niangh Ciang | Sprint 2 | Exercises

Sprint-2/debug/address.js

@@ -1,8 +1,10 @@
-// Predict and explain first...
+/* 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
+My prediction is that when I run this code it will return undefined.
+This is because this is an object not an array, objects are not indexed by numbers, they are indexed by keys. 
+So when i try to access address[0], it will return undefined because there is no key '0' in the address object.
+
+*/
 
 const address = {
   houseNumber: 42,
@@ -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 +1,8 @@
-// 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
+/* Predict and explain first...
+I think this will return an error because of the for...of loop.
+The for...of loop is used to iterate over iterable objects like arrays, strings, maps, sets, etc.
+So this will return an error because the author object is not iterable.
+*/
 
 const author = {
   firstName: "Zadie",
@@ -11,6 +12,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -1,8 +1,10 @@
-// Predict and explain first...
+/* 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?
+This code will log the title and serves correctly, but the ingredients will not be logged on separate lines as intended.
+This happens because the ingredients array is being logged as a whole object, which will not format it correctly.
+The output will for the ingredients will be [object Object] instead of each ingredient on a new line.
+
+ */
 
 const recipe = {
   title: "bruschetta",
@@ -11,5 +13,7 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+  ingredients:`);
+recipe.ingredients.forEach((ingredient) => {
+  console.log(`- ${ingredient}`);
+});

Sprint-2/implement/contains.js

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

Sprint-2/implement/contains.test.js

@@ -20,16 +20,33 @@ 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");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+describe("contains", () => {
+  test("return false when passed an empty object", () => {
+    expect(contains({}, "a")).toEqual(false);
+  });
+
+  // Given an object with properties
+  // When passed to contains with an existing property name
+  // Then it should return true
+  test("return true when passed an object with an existing property name", () => {
+    expect(contains({ a: 1, b: 2 }, "a")).toEqual(true);
+    expect(contains({ apple: 1, banana: 2 }, "banana")).toEqual(true);
+  });
+
+  // Given an object with properties
+  // When passed to contains with a non-existent property name
+  // Then it should return false
+  test("return false when passed an object with a non-existent property name", () => {
+    expect(contains({ a: 1, b: 2 }, "c")).toEqual(false);
+    expect(contains({ apple: 1, banana: 2 }, "orange")).toEqual(false);
+  });
+
+  // Given invalid parameters like an array
+  // When passed to contains
+  // Then it should return false or throw an error
+  test("return false when passed invalid parameters like an array", () => {
+    expect(contains([], "a")).toEqual(false);
+    expect(contains(null, "a")).toEqual(false);
+    expect(contains(undefined, "a")).toEqual(false);
+  });
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,13 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  if (!Array.isArray(countryCurrencyPairs)) {
+    throw new Error("Invalid input");
+  }
+
+  const lookup = {};
+  for (const [country, currency] of countryCurrencyPairs) {
+    lookup[country] = currency;
+  }
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,43 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+describe("createLookup", () => {
+  test("creates a country currency code lookup for a single code", () => {
+    const countryCurrencyPairs = [["US", "USD"]];
+    const expectedLookup = { US: "USD" };
+    expect(createLookup(countryCurrencyPairs)).toEqual(expectedLookup);
+  });
+
+  test("creates a country currency code lookup for multiple codes", () => {
+    const countryCurrencyPairs = [
+      ["US", "USD"],
+      ["CA", "CAD"],
+    ];
+    const expectedLookup = { US: "USD", CA: "CAD" };
+    expect(createLookup(countryCurrencyPairs)).toEqual(expectedLookup);
+  });
+
+  test("returns an empty object when passed an empty array", () => {
+    const countryCurrencyPairs = [];
+    const expectedLookup = {};
+    expect(createLookup(countryCurrencyPairs)).toEqual(expectedLookup);
+  });
+
+  test("throws error for invalid input", () => {
+    expect(() => createLookup(null)).toThrow();
+    expect(() => createLookup(undefined)).toThrow();
+    expect(() => createLookup({})).toThrow();
+  });
+
+  test("returns repeated keys with the last value", () => {
+    const countryCurrencyPairs = [
+      ["US", "USN"],
+      ["CA", "CAD"],
+      ["US", "USD"],
+    ];
+    const expectedLookup = { US: "USD", CA: "CAD" };
+    expect(createLookup(countryCurrencyPairs)).toEqual(expectedLookup);
+  });
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -4,9 +4,18 @@ function parseQueryString(queryString) {
     return queryParams;
   }
   const keyValuePairs = queryString.split("&");
+  const replacePlusWithSpace = (str) => str.replace(/\+/g, " ");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    if (pair === "") continue;
+
+    const [rawKey, ...rawValueParts] = pair.split("=");
+    const keyWithSpaces = replacePlusWithSpace(rawKey || "");
+    const valueWithSpaces = replacePlusWithSpace(rawValueParts.join("=") || "");
+
+    const key = decodeURIComponent(keyWithSpaces);
+    const value = decodeURIComponent(valueWithSpaces);
+
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -3,7 +3,7 @@
 // Below are some test cases the implementation doesn't handle well.
 // Fix the implementation for these tests, 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("should parse values containing '='", () => {
   expect(parseQueryString("equation=a=b-2")).toEqual({
@@ -37,12 +37,6 @@ test("should replace '+' by ' '", () => {
   });
 });
 
-// Stretch exercise: Handling query strings that contain identical keys
-
-// Delete this test if you are not working on this optional case
-test("should store values of a key in an array when the key has 2 or more values", () => {
-  expect(parseQueryString("key=value1&key=value2&key=value3&foo=bar")).toEqual({
-    key: ["value1", "value2", "value3"],
-    foo: "bar",
-  });
+test("should handle duplicate keys", () => {
+  expect(parseQueryString("a=1&a=2")).toEqual({ a: "2" });
 });

Sprint-2/implement/tally.js

@@ -1,3 +1,13 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("Invalid input");
+  }
+
+  const counts = {};
+  for (const item of items) {
+    counts[item] = (counts[item] || 0) + 1;
+  }
+  return counts;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -14,21 +14,38 @@ const tally = require("./tally.js");
  * 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");
+describe("tally", () => {
+  test("returns an empty object for an empty array", () => {
+    expect(tally([])).toEqual({});
+  });
 
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
+  // Given an array with duplicate items
+  // When passed to tally
+  // Then it should return counts for each unique item
+  test("returns counts for each unique item", () => {
+    expect(tally(["apple"])).toEqual({ apple: 1 });
+    expect(tally(["apple", "banana", "orange"])).toEqual({
+      apple: 1,
+      banana: 1,
+      orange: 1,
+    });
+  });
 
-// Given an invalid input like a string
-// When passed to tally
-// Then it should throw an error
+  test("returns counts for each unique item with duplicates", () => {
+    expect(
+      tally(["apple", "banana", "orange", "apple", "banana", "orange"])
+    ).toEqual({ apple: 2, banana: 2, orange: 2 });
+  });
+
+  // Given an invalid input like a string
+  // When passed to tally
+  // Then it should throw an error
+  test("throws an error for invalid input", () => {
+    expect(() => tally("invalid input")).toThrow("Invalid input");
+    expect(() => tally(123)).toThrow("Invalid input");
+    expect(() => tally({})).toThrow("Invalid input");
+  });
+});

Sprint-2/interpret/invert.js

@@ -6,24 +6,46 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
-function invert(obj) {
+/*function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
     invertedObj.key = value;
   }
 
   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 key-value pairs from the object. It's needed to iterate over the object's properties.
 
 // 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 incorrectly using `invertedObj.key` 
+instead of using the actual key and value from the object. It should be using `invertedObj[value] = key;` to correctly
+swap the keys and values.*/
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+function invert(obj) {
+  const invertedObj = {};
+
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    throw new Error("Invalid input");
+  }
+
+  for (const [key, value] of Object.entries(obj)) {
+    invertedObj[value] = key;
+  }
+
+  return invertedObj;
+}
+
+module.exports = invert;

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,24 @@
+const invert = require("./invert");
+
+describe("invert", () => {
+  test("returns an empty object for an empty object", () => {
+    expect(invert({})).toEqual({});
+  });
+
+  test("returns inverted object for a single key-value pair", () => {
+    expect(invert({ a: 1 })).toEqual({ 1: "a" });
+  });
+
+  test("returns inverted object for multiple key-value pairs", () => {
+    expect(invert({ a: 1, b: 2 })).toEqual({ 1: "a", 2: "b" });
+  });
+
+  test("throws an error for invalid input", () => {
+    expect(() => invert(null)).toThrow("Invalid input");
+    expect(() => invert("Number")).toThrow("Invalid input");
+    expect(() => invert(123)).toThrow("Invalid input");
+  });
+  test("returns last key for duplicate values", () => {
+    expect(invert({ a: 1, b: 2, c: 1 })).toEqual({ 1: "c", 2: "b" });
+  });
+});

Sprint-2/stretch/count-words.js

@@ -26,3 +26,20 @@
 
 3. Order the results to find out which word is the most common in the input
 */
+
+function countWords(str) {
+  if (typeof str !== "string") {
+    throw new Error("Invalid input");
+  }
+
+  str = str.replace(/[.,!?]/g, "");
+  str = str.toLowerCase();
+  const words = str.split(" ").filter(Boolean);
+  const result = {};
+
+  for (const word of words) {
+    result[word] = (result[word] || 0) + 1;
+  }
+  const sortedResult = Object.entries(result).sort((a, b) => b[1] - a[1]);
+  return sortedResult;
+}