London | 26-ITP-Jan | Miriam Jorna | Sprint 2 | Data Groups

Sprint-2/debug/address.js

@@ -11,5 +11,7 @@ const address = {
   country: "England",
   postcode: "XYZ 123",
 };
+// not an array so an index number doesn't work
+console.log(`My house number is ${address.houseNumber}`);
+
 
-console.log(`My house number is ${address[0]}`);

Sprint-2/debug/author.js

@@ -11,6 +11,7 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
+//"author" is not iterable. for...of is for arrays, not for objects

Sprint-2/debug/recipe.js

@@ -12,4 +12,7 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`);
+
+// the ${recipe} tries to log everything into one string (and fails).
+// used join to list them separately and on new lines 

Sprint-2/implement/contains.js

@@ -1,3 +1,8 @@
-function contains() {}
+function contains(obj, property) {
+  if (Array.isArray(obj) || typeof obj !== "object" || obj === null) {
+    return false;
+  }
+  return obj.hasOwnProperty(property);
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,16 +20,28 @@ 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 an empty object returns false", () => {
+  expect(contains({}, "a")).toEqual(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("given an object with properties, returns true for existing property", () => {
+  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("given an object with properties, returns false for non-existent property", () => {
+  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("given invalid parameters like an array, returns false", () => {
+  expect(contains([1, 2, 3], "0")).toEqual(false);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,9 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  const lookup = {};
+  for (const [country, currency] of pairs) {
+    lookup[country] = currency;
+  }
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,7 +1,30 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
-
+test("returns an empty object for an empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+test("creates a country currency code lookup for multiple codes", () => {
+  expect(createLookup([['US', 'USD'], ['CA', 'CAD']])).toEqual({
+    'US': 'USD',
+    'CA': 'CAD'
+  });
+});
+
+test("creates a lookup for a single pair", () => {
+  expect(createLookup([['GB', 'GBP']])).toEqual({ 'GB': 'GBP' });
+});
+
+test("creates a lookup for multiple European countries with EUR", () => {
+  expect(createLookup([['NLD', 'EUR'], ['GER', 'EUR'], ['BEL', 'EUR'], ['FRA', 'EUR'], ['ESP', 'EUR'], ['POR', 'EUR']])).toEqual({
+    'NLD': 'EUR',
+    'GER': 'EUR',
+    'BEL': 'EUR',
+    'FRA': 'EUR',
+    'ESP': 'EUR',
+    'POR': 'EUR'
+  });
+});
 /*
 
 Create a lookup object of key value pairs from an array of code pairs

Sprint-2/implement/querystring.js

@@ -6,7 +6,11 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const index = pair.indexOf("=");
+    if (index === -1) continue; // skip pairs with no "="
+    const key = pair.slice(0, index);
+    const value = pair.slice(index + 1);
+    if (key === "") continue; // skip empty keys
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -7,6 +7,25 @@ const parseQueryString = require("./querystring.js")
 
 test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
-  });
+    "equation": "x=y+1" });
+});
+
+  test("parses empty querystring", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses querystring with empty value", () => {
+  expect(parseQueryString("name=")).toEqual({ name: "" });
+});
+
+test("parses querystring values containing =", () => {
+  expect(parseQueryString("equation=x=y+1")).toEqual({ equation: "x=y+1" });
+});
+
+test("parses single key value pair", () => {
+  expect(parseQueryString("name=Ntombi")).toEqual({ name: "Ntombi" });
+});
+
+test("parses multiple key value pairs", () => {
+  expect(parseQueryString("name=Ntombi&age=40")).toEqual({ name: "Ntombi", age: "40" });
 });

Sprint-2/implement/tally.js

@@ -1,3 +1,16 @@
-function tally() {}
+function tally(arr) {
+  if (!Array.isArray(arr)) {
+    throw new Error("Input must be an array");
+  }
+  const result = {};
+  for (const item of arr) {
+   if (Object.hasOwn(result, item)) {
+  result[item]++;
+} else {
+  result[item] = 1;
+}
+    }
+  }
+  return result;
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -23,12 +23,24 @@ 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("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
+
+test("given an array with one item, returns count of 1", () => {
+  expect(tally(['a'])).toEqual({ a: 1 });
+});
 
 // 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 duplicate items returns counts for each type", () => {
+  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("given an invalid input like a string, throws an error", () => {
+  expect(() => tally("invalid")).toThrow();
+});

Sprint-2/interpret/invert.js

@@ -6,24 +6,49 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
-function invert(obj) {
-  const invertedObj = {};
+// leaving original code in for easier referral:
 
-  for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
-  }
+// function invert(obj) {
+//  const invertedObj = {};
+//
+//  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 }
+// the current return value is {key : 1 }
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// the current return value is {key : 2} because the key is overwritten and 
+// only the last value is stored
 
 // 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 converts an object into an array of [key, value] pairs. it is needed because
+// for...of needs an array to work with 
 
 // d) Explain why the current return value is different from the target output
+// invertedObj.key = value creates a literal string with the name "key" instead of the value key.
+// also, the current code assigns "value" to the new property instead of "key" 
 
 // 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;
+}
+
+// Tests
+console.log(invert({ a: 1 })); // Expected output: { "1": "a" }
+console.log(invert({ a: 1, b: 2 })); // Expected output: { "1": "a", "2": "b" }