Glasgow | Jan-26 | Elisabeth Matulian | Sprint 2 | Exercises

Sprint-2/debug/address.js

@@ -1,4 +1,5 @@
 // Predict and explain first...
+//The console.log will log out undefined because there is no such a key as 0 in the address 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 +1,6 @@
 // Predict and explain first...
+//1st prediction: var value will log out both-key and value and we need value only
+//2nd prediction(as the 1st was wrong): MDN says that for...of doen't work with objects but for...in does
 
 // 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 +13,6 @@ 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

@@ -1,4 +1,5 @@
 // Predict and explain first...
+// the issue here is with line 16 ${recipe}. I guess it will log out thw whole content of the recipe object, both key and value. 
 
 // 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 +13,4 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join('\n')}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,7 @@
-function contains() {}
-
-module.exports = contains;
+function contains(object, property) {
+    if (typeof object === 'object' && false === Array.isArray(object)) {
+        return object.hasOwnProperty(property);
+    }
+    else throw new Error("Not an object");
+}
+module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -16,20 +16,33 @@ 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.todo("contains on empty object returns false");
 
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("returns false for empty object", () => {
+    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("returns true for object that contains an existing property name", () => {
+    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("returns false for object that contains a non-existent property name", () => {
+    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("it will throw an error parameters are invalid", () => {
+    expect(() => contains([])).toThrow(Error);
+});
+

Sprint-2/implement/lookup.js

@@ -1,5 +1,10 @@
-function createLookup() {
-  // implementation here
+function createLookup(array) {
+  let object = {};
+  for (const pair of array) {
+    object[pair[0]] = pair[1];
+  }
+  return object
 }
 
 module.exports = createLookup;
+

Sprint-2/implement/lookup.test.js

@@ -1,7 +1,9 @@
 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'});
+});
 /*
 
 Create a lookup object of key value pairs from an array of code pairs

Sprint-2/implement/querystring.js

@@ -6,8 +6,12 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (pair.includes('=')){
+      const index = pair.indexOf("=");
+      const key = pair.slice(0, index);
+      const value = pair.slice(index+1);
+      queryParams[key] = value;
+    }
   }
 
   return queryParams;

Sprint-2/implement/querystring.test.js

@@ -10,3 +10,16 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+
+test("parses querystring values doesn't contain =", () => {
+  expect(parseQueryString("equationxy1")).toEqual({});
+});
+
+test("given a query string with no query parameters, returns an empty object", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("given a query string with multiple key-value pairs, returns them in object form", () => {
+  expect(parseQueryString("sort=lowest&colour=yellow")).toEqual({sort: "lowest", colour: "yellow"});
+});
+

Sprint-2/implement/tally.js

@@ -1,3 +1,14 @@
-function tally() {}
+function tally(array) {
+    let object = {};
+    if (Array.isArray(array)) {
+        for (const i of array) {
+            if (object.hasOwnProperty(i)) {
+                object[i] = object[i] + 1;
+            }
+            else object[i] = 1;
+        }
+    return object;}
+    else throw new Error("Invalid input");
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,12 +23,21 @@ 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");
+test("returns an empty object when array is empty", () => {
+    expect(tally([])).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 when an array with duplicate items", () => {
+    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("throw an error when input not an array", () => {
+    expect(() => tally('a', 'a', 'b', 'c')).toThrow(Error);
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,30 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+
 // a) What is the current return value when invert is called with { a : 1 }
+// invertedObj.key = value; this line creates a key literally with name "key". it returns {key : 1}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// every time it meets the key and reassign it, so {key : 2}
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// to swap pair key-value with each other. should return {1 : a, 2: b}
 
 // c) What does Object.entries return? Why is it needed in this program?
+// it returns key-value pairs in arrays nested of array. we need Object.entries to convert key-value pairs to array because for..of doesn't work with objects. 
+//I wonder if we could solve the function by swapping key-value using [key, value] = [value, key] in some way? p.s. I'll delete this comment after review:)
 
 // d) Explain why the current return value is different from the target output
+// invertedObj.key = value; this line creates a key literally with name "key". it returns {key : 1}
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+
+module.exports = invert;

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,6 @@
+const invert = require("./invert.js");
+
+
+test(" should return an object with swapped keys and values", () => {
+    expect(invert({"a" : "1", "b": "2"})).toEqual({"1" : "a", "2" : "b"});
+});