Sheffield | ITP-Jan-26 | Hayriye Saricicek | Sprint 2 | Module-Data-Groups

Sprint-2/debug/address.js

@@ -1,4 +1,5 @@
-// Predict and explain first...
+// I predict it will cause an error at console.log because it is wanting to print address[0] but
+// address is not an array it is an object...
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +13,4 @@ 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

@@ -1,4 +1,5 @@
-// Predict and explain first...
+// the for ... of only works when iterating through data and this is not what is required
+// it will cause an error
 
 // 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 +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

@@ -1,4 +1,4 @@
-// Predict and explain first...
+// Didn't put recipe.ingredients in console.log so will cause error because cannot access recipe
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -12,4 +12,4 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,8 @@
-function contains() {}
+function contains(obj, key) {
+  if (!obj || typeof obj !== "object" || Array.isArray(obj)) {
+    throw new Error("Input must be a non-null object and not an array");
+  }
+  return key in obj; // simply checks if the key exists in the object
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -13,23 +13,42 @@ as the object doesn't contains a key of 'c'
 
 // Acceptance criteria:
 
-// 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
-
-// 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.each([
+    // 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
+
+    // Given an empty object
+    // When passed to contains
+    // Then it should return false
+
+    { input: [{}, "a"], expected: false },
+
+    // Given an object with properties
+    // When passed to contains with an existing property name
+    // Then it should return true
+
+    { input: [{ a: 1, b: 2 }, "a"], expected: true },
+
+    // Given an object with properties
+    // When passed to contains with a non-existent property name
+    // Then it should return false
+
+    { input: [{ a: 1, b: 2 }, "c"], expected: false },
+
+    // Given invalid parameters like an array
+    // When passed to contains
+    // Then it should return false or throw an error
+  ])("finds object contains properties", ({ input, expected }) => {
+    expect(contains(...input)).toBe(expected);
+  });
+  test("throws error when input is null or an array", () => {
+    expect(() => contains(null, "a")).toThrow(
+      "Input must be a non-null object and not an array"
+    );
+    expect(() => contains(["a", "b"], "a")).toThrow(
+      "Input must be a non-null object and not an array"
+    );
+});
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,10 @@
-function createLookup() {
-  // implementation here
-}
+function createLookup(CountryCurrencyPairs) {
+  const result = {};
 
+  for (const pair of CountryCurrencyPairs) {
+    const [country, currency] = pair;
+    result[country] = currency;
+  }
+  return result;
+}
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,10 +1,20 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("creates lookup object", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
 
-/*
+  const result = createLookup(input);
 
-Create a lookup object of key value pairs from an array of code pairs
+  expect(result).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
+
+/*Create a lookup object of key value pairs from an array of code pairs
 
 Acceptance Criteria:
 

Sprint-2/implement/querystring.js

@@ -6,7 +6,8 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const [key, ...rest] = pair.split("=");
+    const value = rest.join("=");
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -5,6 +5,24 @@
 
 const parseQueryString = require("./querystring.js")
 
+
+  test("returns empty object for empty string", () => {
+    expect(parseQueryString("")).toEqual({});
+  });
+
+  test("parses a single key-value pair", () => {
+    expect(parseQueryString("name=John")).toEqual({
+      name: "John",
+    });
+  });
+
+  test("parses multiple key-value pairs", () => {
+    expect(parseQueryString("name=John&age=30")).toEqual({
+      name: "John",
+      age: "30",
+    });
+  });
+
 test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
     "equation": "x=y+1",

Sprint-2/implement/tally.js

@@ -1,3 +1,18 @@
-function tally() {}
+function tally(arr) {
+  if (!Array.isArray(arr)) {
+    throw new Error("Input must be an array"); //checks input is an array if not throws error
+  }
 
+  const result = Object.create(null); //creates an empty object without a prototype to avoid issues with inherited properties
+
+  for (const item of arr) {
+    if (item in result) {
+      result[item] = result[item] + 1;
+    } else {
+      result[item] = 1;
+    }
+  }
+
+  return result;
+}
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -20,15 +20,29 @@ const tally = require("./tally.js");
 // 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");
-
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
-
-// Given an invalid input like a string
-// When passed to tally
-// Then it should throw an error
+describe("tally", () => {
+  test.each([
+    // Given an empty array
+    // When passed to tally
+    // Then it should return an empty object
+
+    { input: [], expected: {} },
+
+    // Given an array with duplicate items
+    // When passed to tally
+    // Then it should return counts for each unique item
+
+    { input: ["a", "b", "a"], expected: { a: 2, b: 1 } },
+
+    // Given an invalid input like a string
+    // When passed to tally
+    // Then it should throw an error
+
+    { input: ["toString", "toString"], expected: { toString: 2 } }, // new test
+  ])("counts items correctly", ({ input, expected }) => {
+    expect(tally(input)).toEqual(expected);
+  });
+  test("throws error for invalid input", () => {
+    expect(() => tally("not an array")).toThrow("Input must be an array");
+  });
+});

Sprint-2/interpret/invert.js

@@ -6,24 +6,51 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
-function invert(obj) {
-  const invertedObj = {};
+//function invert(obj) {
+//  const invertedObj = {};
 
-  for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
-  }
+//  for (const [key, value] of Object.entries(obj)) {
+//    invertedObj.key = value;
+//  }
 
-  return invertedObj;
-}
+//  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 the object in pairs [key, value]. It is needed in this program
+  to iterate through the object and access both the key and value at the same time, which is necessary
+   for swapping them in the inverted object. */
 
 // 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 implementation of the invert 
+function is incorrect. Instead of using the variable key to set the property in the inverted object, 
+it is using the literal string "key". This means that every time a key-value pair is processed, 
+it overwrites the same property "key" in the inverted object, resulting in only the last key-value 
+pair being stored. To fix this, we need to use bracket notation to set the property in the inverted object 
+using the value as the key and the key as the value.*/
+
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+function invert(obj) {
+  const invertedObj = {};
+
+  for (const [key, value] of Object.entries(obj)) {
+    invertedObj[value] = key;
+  }
+
+  return invertedObj;
+}
+
+console.log(invert({ a: 1 })); // { "1": "a" }
+console.log(invert({ a: 1, b: 2 })); // { "1": "a", "2": "b" }
+console.log(invert({ x: 10, y: 20 })); // { "10": "x", "20": "y" }