Manchester | ITP-May-2025 | Chukwuemeke Ajuebor | Sprint 2 | Data-Groups

Sprint-2/debug/address.js

@@ -4,6 +4,8 @@
 // but it isn't working...
 // Fix anything that isn't working
 
+// it won't work because this is an object literal with key-value pairs
+
 const address = {
   houseNumber: 42,
   street: "Imaginary Road",
@@ -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

@@ -11,6 +11,9 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const val in author) {
+  console.log(author[val]);
 }
+// Changing value to val so it does not conflict with fact that it is the keys that are being logged to 
+// display the 'value' they hold
+//Used for .... in  as this will iterate over the keys ie the indexes rather than the values

Sprint-2/debug/recipe.js

@@ -11,5 +11,9 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+  ingredients:`);
+  for (const items of recipe.ingredients) {
+  console.log(items);
+};
+//we have to use for...of as it will loop directly over values of the array 
+// rather than the for ... in which will loop over the indexes.

Sprint-2/implement/contains.js

@@ -1,3 +1,15 @@
-function contains() {}
+function contains(obj,item) {
+    if (obj === null || typeof obj !== 'object' || Array.isArray(obj)) {
+    return false;
+  }
+
+  if (typeof item !== 'string') {
+    return false;
+  } 
+
+  // this checks that the property exists in the object
+  return obj.hasOwnProperty(item);
+}
+
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,7 +20,6 @@ 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
@@ -33,3 +32,21 @@ test.todo("contains on empty object returns false");
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+
+describe('contains', () => {
+  test('returns false when given an empty object', () => {
+    expect(contains({}, 'a')).toBe(false);
+  });
+
+  test('returns true if the object has the property', () => {
+    expect(contains({ a: 1, b: 2, c: 3, d: 4 }, 'a')).toBe(true);
+  });
+
+  test('returns false if the object does not have the property', () => {
+    expect(contains({ a: 1, b: 2, c: 3 }, 'e')).toBe(false);
+  });
+
+  test('should return false when passed an array', () => {
+    expect(contains([1, 2, 3], 'a')).toBe(false);
+  });
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,14 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  let lookup = {}; //begins with an empty object to populate
+
+  for (let pair of countryCurrencyPairs) {
+    let country = pair[0];   
+    let currency = pair[1];
+
+    lookup[country] = currency;
+  }
+//this iterates through all pairs returning them into the created empty object
+  return lookup; 
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,24 @@
 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 pairs = [
+    ['US', 'USD'],
+    ['CA', 'CAD'],
+    ['GB', 'GBP'],
+    ['JP', 'JPY'],
+    ['IN', 'INR'],
+  ];
+
+  const expected = {
+    US: 'USD',
+    CA: 'CAD',
+    GB: 'GBP',
+    JP: 'JPY',
+    IN: 'INR',
+  };
+
+  expect(createLookup(pairs)).toEqual(expected);
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -5,8 +5,21 @@ function parseQueryString(queryString) {
   }
   const keyValuePairs = queryString.split("&");
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+  for (let i = 0; i < keyValuePairs.length; i++) {
+    const pair = keyValuePairs[i];
+    const equalIndex = pair.indexOf("=");
+
+    let key, value;
+
+    if (equalIndex === -1) {
+      key = pair;
+      value = "";
+    } // if no "=" is found key is assigned with a value of empty string
+    else {
+      key = pair.substring(0, equalIndex);
+      value = pair.substring(equalIndex + 1);
+    } // Split into key and value for as many "=" in the value using substring
+
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -6,7 +6,28 @@
 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")).toEqual({"equation": "x=y+1"})
+});
+test("returns empty object for empty query string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses single key=value pair", () => {
+  expect(parseQueryString("a=1")).toEqual({ a: "1" });
+});
+
+test("parses multiple key=value pairs", () => {
+  expect(parseQueryString("a=1&b=2&c=3")).toEqual({
+    a: "1",
+    b: "2",
+    c: "3",
   });
 });
+
+test("parses key without value (assigns empty string)", () => {
+  expect(parseQueryString("a=&b=2")).toEqual({a: "", b: "2"});
+});
+
+test("handles key with no '=' at all", () => {
+  expect(parseQueryString("hello")).toEqual({hello: ""});
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,21 @@
-function tally() {}
+function tally(arr) {
+    if (!Array.isArray(arr)) {
+    throw new Error("Input an array!");
+  }
+
+  const counts = {};
+
+  for (let i = 0; i < arr.length; i++) {
+    const item = arr[i];
+    if (counts[item]) {
+      counts[item] += 1;
+    } else {
+      counts[item] = 1;
+    }// if/else ensures add to the count of an item if it has been
+    // counted in a previous iteration or start at 1.  
+  }
+
+  return counts;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,7 +23,7 @@ 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.todo("tally on an empty array returns an empty object");
 
 // Given an array with duplicate items
 // When passed to tally
@@ -32,3 +32,29 @@ test.todo("tally on an empty array returns an empty object");
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+
+describe("tally function", () => {
+  test("tally on an empty array returns an empty object", () => {
+    expect(tally([])).toEqual({});
+  });
+
+  test("tally on an array with one item", () => {
+    expect(tally(["a"])).toEqual({ a: 1 });
+  });
+
+  test("tally on an array with duplicate items", () => {
+    expect(tally(["a", "a", "a"])).toEqual({ a: 3 });
+  });
+
+  test("tally on an array with multiple different items", () => {
+    expect(tally(["a", "a", "a", "b", "b", "c"])).toEqual({ a: 3, b: 2, c: 1 });
+  });
+
+  test("tally throws an error for a string input", () => {
+    expect(() => tally("not an array")).toThrow("Input an array!");
+  });
+
+  test("tally throws an error for an object input", () => {
+    expect(() => tally({ a: 1 })).toThrow("Input an array!");
+  });
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,31 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+module.exports = invert;
+
 // a) What is the current return value when invert is called with { a : 1 }
+    // the current return will take the value in the key value pair using Object.entries and  
+    // and assign it to a property called key returning {key:1}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+    //after the first loop, second iteration reassigns the value to 
+    //the property called key returning {key:2}
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+    // it should give {"1": "a", "2": "b" }
 
 // c) What does Object.entries return? Why is it needed in this program?
+    //this function allows for iteration over both keys and values at once
+    // instead of looping over them seperately.
 
 // d) Explain why the current return value is different from the target output
+    //for the target output, we want the property name to be the set to the value 
+    // of the original key-value pair.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,9 @@
+const invert = require("./invert.js");
+
+test("inverts a single key-value pair", () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+test("inverts multiple unique key-value pairs", () => {
+  expect(invert({ x: 3, y: 4 })).toEqual({ "3": "x", "4": "y" });
+});