ITP-Jan | NW | Jovy So | Module-Data-Groups | WEEK 2

Sprint-2/debug/address.js

@@ -12,4 +12,7 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+// console.log(`My house number is ${address[0]}`);
+// Predict result: My house number is undefined. As address[0] is undefined. 
+
+console.log(`My house number is ${address["houseNumber"]}`);

Sprint-2/debug/author.js

@@ -11,6 +11,12 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+// for (const value of author) {
+//   console.log(value);
+// }
+
+// Predict: Will get error because for..of loop works only on Iterables
+
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -10,6 +10,13 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+// console.log(`${recipe.title} serves ${recipe.serves}
+//   ingredients:
+// ${recipe}`);
+
+// console.log(`${recipe}`);
+//Predict result: bruschetta serves 2 ingredients: [object Object]
+
+console.log(`${recipe.title} 
+serves ${recipe.serves}
+ingredients: ${recipe.ingredients}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,15 @@
-function contains() {}
+function contains(object, propertyName) {
+  // console.log(propertyName, '<-- property name');
+  if (!propertyName) return false;
+  if (!object) return false;
+  if (object.hasOwnProperty(propertyName)) return true;
+  else return false;
+};
 
 module.exports = contains;
+
+console.log(contains({a: 1, b: 2}, 'a'));
+console.log(contains({a: 1, b: 2}));
+console.log(contains());
+console.log(contains({a: 1, b: 2}, 'c'));
+console.log(contains([1,2,3]));

Sprint-2/implement/contains.test.js

@@ -16,20 +16,38 @@ 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
+test("given an object and property arg returns true", () => {
+  expect(contains({a: 1, b: 2}, 'a')).toEqual(true);
+});
+
+test("given an object, but no property arg then returns false", () => {
+expect(contains({a: 1, b: 2})).toEqual(false);
+});
 
 // 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()).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("contains the property in the object returns true", () => {
+  expect(contains({a: 1, b: 2}, 'a')).toEqual(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("not contains the property in the object returns false", () => {
+  expect(contains({a: 1, b: 2}, 'c')).toEqual(false);
+});
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("contains invalid parameters return false", () => {
+  expect(contains([1,2,3])).toEqual(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,8 @@
-function createLookup() {
+function createLookup(countryCurrencyPairs) {
   // implementation here
-}
+  if (countryCurrencyPairs !== undefined) return Object.fromEntries(countryCurrencyPairs);
+};
 
 module.exports = createLookup;
+
+console.log(createLookup([['US', 'USD'], ['CA', 'CAD'], ["HK", 'HKD']]));

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,11 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+// test.todo("creates a country currency code lookup for multiple codes");
+
+test("creates a country currency code lookup for multiple codes", () => {
+  expect(createLookup([['US', 'USD'], ['CA', 'CAD']])).toEqual({'US': 'USD','CA': 'CAD'});
+});
+
 
 /*
 

Sprint-2/implement/querystring.js

@@ -6,11 +6,13 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const [key, value] = pair.split(/=(.*)/s);
     queryParams[key] = value;
   }
 
   return queryParams;
 }
 
 module.exports = parseQueryString;
+
+console.log(parseQueryString("equation=x=y+1"));

Sprint-2/implement/querystring.test.js

@@ -10,3 +10,4 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+

Sprint-2/implement/tally.js

@@ -1,3 +1,16 @@
-function tally() {}
+function tally(items) {
+  let countLetter = {};
+  if (Array.isArray(items) === false) throw new Error("You must provide an item");
+  else if (items.length === 0) return countLetter;
+  else {
+    items.forEach(letter => countLetter[letter] ? countLetter[letter]++ : countLetter[letter] = 1) 
+    return countLetter;
+  };
+};
 
 module.exports = tally;
+
+console.log(tally(['a', 'a', 'a'])); // output: { a: 3 }
+console.log(tally(['a', 'b', 'c'])); // output: { a: 1, b: 1, c: 1 }
+console.log(tally([])); // output: {}
+// console.log(tally('Hello')); // output: Throw Error "You must provide an item"

Sprint-2/implement/tally.test.js

@@ -19,16 +19,31 @@ 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 each unique item on an array returns the count", () => {
+  expect(tally(['a', 'b', 'c'])).toEqual({ a: 1, b: 1, c: 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 each unique item on an array with duplicate items returns the count for each unique item", () => {
+  expect(tally(['a', 'a', 'a'])).toEqual({ a: 3 });
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("Given an invalid input throw an error", () => {
+  expect( () => { tally('Hello') } ).toThrow("You must provide an item");
+});
+

Sprint-2/interpret/invert.js

@@ -10,20 +10,34 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+module.exports = invert;
+
+console.log(invert({x : 10, y : 20})); //output: {"10": "x", "20": "y"}
+console.log(invert({ a: 1, b: 2 })); // output: {"1": "a", "2": "b"}
+
 // 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 key/pairs of an object, it makes it simple to use objects in loops.
+// In this case, if Object.entries is removed, it would occur error showing obj is not iterable.
+// Therefore, Object.entries is needed as it changed obj to array so that it can be looped over.
 
 // d) Explain why the current return value is different from the target output
+// There are two problems in the current function
+// 1. key and value haven't been swap
+// 2. invertedObj.key is unable to return the key of the object
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,5 @@
+const invert = require("./invert.js");
+
+test("Given an object, then swap the keys and values in the object", () => {
+  expect(invert({x : 10, y : 20})).toEqual({"10": "x", "20": "y"});
+});