Birmingham | ITP-Sep-25 | Ahmad Ehsas | sprint 2 | Data groups

Sprint-2/debug/address.js

@@ -1,4 +1,5 @@
 // Predict and explain first...
+// The bellow code should be in array format.
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +13,7 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+//console.log(`My house number is ${address[0]}`);
+
+// Here we use dot notation to access the houseNumber property
+console.log(`My house number is ${address.houseNumber}`);

Sprint-2/debug/author.js

@@ -1,4 +1,6 @@
 // Predict and explain first...
+// In this code, we are trying to iterate over the values of an object using " for ... of loop".
+// However, the `for ... of` loop is designed to iterate over iterable objects like arrays, not objects.
 
 // 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
@@ -11,6 +13,16 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+// for this code we use `for ... in` loop method whenever we want to loop though an object.
+// The `for ... in` loop iterates through properties in the prototype chain.
+// This means that we need to check if the property belongs to the object using hasownproperty whenever we loop through an object with the `for ... in` loop.
+
+for (const key in author) {
+  if (author.hasOwnProperty(key)) {
+    console.log(`${key}: ${author[key]}`);
+  }
 }
+
+//for (const value of author) {
+// console.log(value);
+//}

Sprint-2/debug/recipe.js

@@ -1,4 +1,5 @@
 // Predict and explain first...
+// we should add new line `\n` between ingredients to log them on a new line.
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -10,6 +11,13 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+// Here we add `join("\n") to the ingredients array to log each ingredient in a new line.
+console.log(
+  `${recipe.title} serves ${
+    recipe.serves
+  } ingredients: ${recipe.ingredients.join("\n")}`
+);
+
+//console.log(`${recipe.title} serves ${recipe.serves}
+// ingredients:
+//${recipe}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,16 @@
-function contains() {}
+function contains(obj, prop) {
+  return obj.hasOwnProperty(prop);
+}
+
+// Or we can use `for ...in loop to check for the property
+// function contains(obj, prop) {
+//   for (const key in obj){
+//    if (key === prop) return true;
+//   }
+//   return false;
+// }
+
+console.log(contains({ a: 1, b: 2 }, "a")); // true
+console.log(contains({ a: 1, b: 2 }, "c")); // false
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,16 +20,35 @@ 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("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 on object with existing property returns true", () => {
+  expect(contains({ a: 1, b: 2 }, "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 on object with non-existent property returns false", () => {
+  expect(contains({ a: 1, b: 2 }, "c")).toBe(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("contains on an array returns false", () => {
+  expect(contains([1, 2, 3], 4)).toBe(false);
+});
+
+test("contains on an array of length returns true", () => {
+  expect(contains([1, 2, 3, 4], "length")).toBe(true);
+}); // the test returns true because 'length' is a property of the array object
+
+test("contains given on array as input return false", () => {
+  expect(contains([1, 2, 3], "a")).toBe(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,16 @@
-function createLookup() {
-  // implementation here
+function createLookup(codePairs) {
+  const lookup = codePairs.reduce((acc, [key, value]) => {
+    acc[key] = value;
+    return acc;
+  }, {});
+  return lookup;
 }
 
+console.log(
+  createLookup([
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ])
+);
+
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,18 @@
 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", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const expectedOutput = {
+    US: "USD",
+    CA: "CAD",
+  };
+
+  expect(createLookup(input)).toEqual(expectedOutput);
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -6,7 +6,7 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const [key, value] = pair.split(/=(.+)/); // We use regex to split only at first.
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -3,10 +3,21 @@
 // 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",
+  expect(parseQueryString("equation=x=y+1")).toStrictEqual({
+    equation: "x=y+1",
+  });
+});
+
+test("returns empty object for empty query string", () => {
+  expect(parseQueryString("")).toStrictEqual({});
+});
+
+test("parses multiple parameters", () => {
+  expect(parseQueryString("name=John&age=30")).toStrictEqual({
+    name: "John",
+    age: "30",
   });
 });

Sprint-2/implement/tally.js

@@ -1,3 +1,19 @@
-function tally() {}
+function tally(array) {
+  if (!Array.isArray(array)) {
+    throw new Error("Input must be an array");
+    // check if the input ia an array. if not, throw an error.
+  }
+  const tally = {};
+
+  for (const item of array) {
+    tally[item] = (tally[item] || 0) + 1;
+    // If the item already exists in tally, increase its count by 1.
+    // If it doesn't exist, start from 1.
+  }
+
+  return tally;
+}
+
+console.log(tally(["a", "a", "a"]));
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -19,16 +19,27 @@ 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("tally on a single item returns count of 1", () => {
+  expect(tally(["a"])).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("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 duplicates 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 on a string throws an error", () => {
+  expect(() => tally("a")).toThrow("Input must be an array");
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,29 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
+console.log(invert({ a: 1 })); // {1: "a"}
+console.log(invert({ a: 1, b: 2 })); // {1: "a", 2: "b"}
+module.exports = invert;
 
 // a) What is the current return value when invert is called with { a : 1 }
+// The current return value is {1: "a"}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// The current return value is {1: "a", 2: "b"}
 
 // 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 takes an object and return an array of key-value pairs.
+// it needed because it converts the object into an array of [key, value] pairs which makes it easy to loop over both key and value at the same time.
 
 // d) Explain why the current return value is different from the target output
+// because it returns the [key, value] of an object in reverse order [value,key]
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,14 @@
+const invert = require("./invert.js");
+
+test("inverts an object with unique keys", () => {
+  expect(invert({ a: 1, b: 2 })).toStrictEqual({ 1: "a", 2: "b" });
+});
+
+test("inverts an object with string keys", () => {
+  // prettier-ignore
+  expect(invert({ cat: "meow", dog: "bark" })).toStrictEqual({ meow: "cat", bark: "dog"});
+});
+
+test("inverts an empty object", () => {
+  expect(invert({})).toEqual({});
+});