Birmingham | ITP-Jan | Roman Sanaye | Sprint 2 | Exercises

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

@@ -3,6 +3,9 @@
 // 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
 
+// ==> this code is looping through an object and only return the key not the value.
+// ==> After testing I found that (for of) does not loop directly in objects and it was throwing error "author is not iterable". In this case we should use (for in) to iterate.
+
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +14,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const value in author) {
+  console.log(author[value]);
 }

Sprint-2/debug/recipe.js

@@ -1,8 +1,10 @@
 // Predict and explain first...
+// ==> this code is not correct as the ingredients act as string not an object key therefore we wont have the value.
 
 // 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?
+// ==> to fix the issue and print each ingredients in new line we need to loop through the array inside our recipe object.
 
 const recipe = {
   title: "bruschetta",
@@ -11,5 +13,7 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:`);
+for (let fruits of recipe.ingredients) {
+  console.log(fruits);
+}

Sprint-2/implement/contains.js

@@ -1,3 +1,18 @@
-function contains() {}
+// start your function
+
+function contains(object, key) {
+  if (Array.isArray(object) && Object.keys(object).length === 0) {
+    return false;
+  } else if (object.hasOwnProperty(key)) {
+    return true;
+  } else return false;
+}
+
+let key = "name";
+const object = {
+  name: "Roman",
+  age: 33,
+  city: "Birmingham",
+};
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -15,21 +15,51 @@ as the object doesn't contains a key of 'c'
 
 // 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
+// Then it should return true if the object contains the property,
+test("It return true when the object contains the property", () => {
+  let object = { name: "Roman", age: 34 };
+  let key = "name";
+  expect(contains(object, key)).toEqual(true);
+});
+// object does not contain the property
+test("It return false when the object does not contains the property", () => {
+  let object = { name: "Roman", age: 34 };
+  let key = "lastName";
+  expect(contains(object, key)).toEqual(false);
+});
 
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("It return false when the object has not any property", () => {
+  let object = {};
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("It returns true when the object has the specified property", () => {
+  const object = { name: "Roman", age: 34, city: "Birmingham" };
+  const key = "name";
+  expect(contains(object, key)).toEqual(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("It returns false when the object does NOT have the specified property", () => {
+  const object = { name: "Roman", age: 34, city: "Birmingham" };
+  const key = "lastName";
+  expect(contains(object, key)).toEqual(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("It return false when an array is passed instead of object", () => {
+  let object = [1, 2, 3];
+  let key = "name";
+  expect(contains(object, key)).toEqual(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,15 @@
-function createLookup() {
-  // implementation here
+// start your function;
+function createLookup(input) {
+  let output = {};
+  for (let pair of input) {
+    let key = pair[0];
+    let value = pair[1];
+    output[key] = value;
+  }
+  return output;
 }
-
+let input = [
+  ["US", "USD"],
+  ["CA", "CAD"],
+];
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,9 +1,7 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
-
 /*
-
+ 
 Create a lookup object of key value pairs from an array of code pairs
 
 Acceptance Criteria:
@@ -33,3 +31,17 @@ It should return:
    'CA': 'CAD'
  }
 */
+
+test("creates a country currency code lookup for multiple codes", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const expected = {
+    US: "USD",
+    CA: "CAD",
+  };
+
+  expect(createLookup(input)).toEqual(expected);
+});

Sprint-2/implement/querystring.js

@@ -1,16 +1,24 @@
+// start your function;
 function parseQueryString(queryString) {
   const queryParams = {};
   if (queryString.length === 0) {
     return queryParams;
   }
-  const keyValuePairs = queryString.split("&");
-
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+  // URLSearchParams is a built-in JavaScript object that can read query strings.
+  const params = new URLSearchParams(queryString); // params stores the query string internally as key-value pairs.
+  for (let pair of params) {
+    let key = pair[0];
+    let value = pair[1];
+    queryParams[key] = value.replace(/ /g, "+");
   }
-
   return queryParams;
 }
+let queryString = "equation=x=y+1";
 
 module.exports = parseQueryString;
+
+// Notice: ===>  URLSearchParams is a class, not a plain function.
+// Classes in JS must be called with new.
+// new URLSearchParams(...) → creates a new instance (object) of the class.
+// That instance knows how to store and iterate key-value pairs.
+// URLSearchParams decodes URL-encoded characters, and in query strings, a + represents a space. and this is why we need .replace(/ /g, "+");

Sprint-2/implement/querystring.test.js

@@ -3,10 +3,10 @@
 // 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",
   });
 });

Sprint-2/implement/tally.js

@@ -1,3 +1,15 @@
-function tally() {}
-
+function tally(arr) {
+  let output = {};
+  if (!Array.isArray(arr)) {
+    throw new Error("Invalid input");
+  } else if (arr.length === 0) {
+    return output;
+  }
+  for (let item of arr) {
+    let count = arr.filter((x) => x === item).length;
+    output[item] = count;
+  }
+  return output;
+}
+let arr = ["a", "b"];
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -19,16 +19,30 @@ const tally = require("./tally.js");
 // Given a function called tally
 // When passed an array of items
 // Then it should return an object containing the count for each unique item
+test("returns count 1 for a single item", () => {
+  const arr = ["a"];
+  expect(tally(arr)).toEqual({ a: 1 });
+});
 
 // 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("returns an empty object when given an empty array", () => {
+  const arr = [];
+  expect(tally(arr)).toEqual({});
+});
 
 // 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 for given duplicate items ", () => {
+  const arr = ["a", "a", "b", "c"];
+  expect(tally(arr)).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("it throw an error if given a string", () => {
+  const str = "a";
+  expect(() => tally(str)).toThrowError();
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,27 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
-
+obj = { a: 1, b: 2 };
+module.exports = invert;
 // a) What is the current return value when invert is called with { a : 1 }
+// answer ===> the output will be {"key": 1}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// answer ===> the output ll be {"key": 2}
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// answer ===> the output ll be {"1": "a", "2": "b"};
 
 // c) What does Object.entries return? Why is it needed in this program?
+// answer ===> converts an object into an array of key-value pairs, we need it to loop through and access the elements.
 
 // d) Explain why the current return value is different from the target output
+// answer ===>  because of this line --> invertedObj.key = value; as it creates a "key" and assign the value to it. and with variables we need to use bracket notation not dot notation.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+// I have fixed the implementation: from invertedObj.key = value to invertedObj[value] = key;

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,13 @@
+const invert = require("./invert.js");
+// testing time
+test("Empty object returns empty object", () => {
+  expect(invert({})).toEqual({});
+});
+
+test("Single key-value pair", () => {
+  expect(invert({ a: 1 })).toEqual({ 1: "a" });
+});
+
+test("Given an object, then it should swap the keys and values in the object", () => {
+  expect(invert({ x: 10, y: 20 })).toEqual({ 10: "x", 20: "y" });
+});

Sprint-2/stretch/count-words.js

@@ -12,6 +12,8 @@
 
   countWords("you and me and you") then the target output is { you: 2, and: 2, me: 1 }
 
+
+
   To complete this exercise you should understand
     - Strings and string manipulation
     - Loops
@@ -26,3 +28,16 @@
 
 3. Order the results to find out which word is the most common in the input
 */
+function countWords(str) {
+  let cleanStr = str.split(" ");
+  let objWords = {};
+  for (let word of cleanStr) {
+    if (word !== "") continue;
+    if (objWords[word]) {
+      objWords[word]++;
+    } else {
+      objWords[word] = 1;
+    }
+  }
+  return objWords;
+}

Sprint-2/stretch/mode.js

@@ -9,28 +9,29 @@
 // into smaller functions using the stages above
 
 function calculateMode(list) {
-  // track frequency of each value
-  let freqs = new Map();
-
+  // Stage 1: Count frequencies
+  let freqs = {};
   for (let num of list) {
-    if (typeof num !== "number") {
-      continue;
-    }
+    if (typeof num !== "number") continue; // skip non-number values
 
-    freqs.set(num, (freqs.get(num) || 0) + 1);
+    if (freqs[num] === undefined) {
+      freqs[num] = 1;
+    } else {
+      freqs[num] += 1;
+    }
   }
-
-  // Find the value with the highest frequency
+  // Stage 2: Find the value with the highest frequency
   let maxFreq = 0;
-  let mode;
-  for (let [num, freq] of freqs) {
-    if (freq > maxFreq) {
-      mode = num;
-      maxFreq = freq;
+  let mode = null;
+
+  for (let num in freqs) {
+    if (freqs[num] > maxFreq) {
+      maxFreq = freqs[num];
+      mode = Number(num); // convert string key to number
     }
   }
 
-  return maxFreq === 0 ? NaN : mode;
+  return mode;
 }
 
 module.exports = calculateMode;