Glasgow | 25-ITP-SEP | Fare Bakhet | Sprint 2 | Coursework/sprint 2

Sprint-2/debug/address.js

@@ -1,4 +1,7 @@
 // Predict and explain first...
+//Prediction: The will be an error at ${address[0]}.
+//Explanation: calling an object using the index as in array. Instead we should use the dot method(.address) or the brackets["address"].
+
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +15,4 @@ 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...
+// Prediction: Going to shows an error in the for loop.
+// Explanation: we should have used the for .. in method (The for...in statement iterates over all enumerable string properties of an object (ignoring properties keyed by symbols), including inherited enumerable properties.)
 
 // 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(`${value}: ${author[value]}`);
 }

Sprint-2/debug/recipe.js

@@ -1,4 +1,6 @@
 // Predict and explain first...
+// Prediction: An error in logging out the ingredients.
+// Explanation: Because of the way to get the value or an element from an array should used the dot notation for example and reach each element using its index.
 
 // 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 +14,7 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients[0]}
+${recipe.ingredients[1]}
+${recipe.ingredients[2]}
+${recipe.ingredients[3]}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,9 @@
-function contains() {}
+function contains(input, propertyName) {
+    if (input && typeof input === 'object' && !Array.isArray(input)) {
+        return input.hasOwnProperty(propertyName);
+    }
+    return false;
+
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -17,19 +17,63 @@ as the object doesn't contains a key of 'c'
 // 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 contains a property name, returns true", function (){
+    const input = {a: 1, b: 2};
+    const propertyName = 'a';
+    const currentOutput = contains(input, propertyName);
+    const targetOutput = true;
+
+    expect(currentOutput).toEqual(targetOutput);
+});
+
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+
+test("given an empty object, returns false", function (){
+    const input = {};
+    const propertyName = 'a';
+    const currentOutput = contains(input, propertyName);
+    const targetOutput = false;
+
+    expect(currentOutput).toEqual(targetOutput);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
 
+test("given an object contains a property name, returns true", function (){
+    const input = {a: 1, b: 2};
+    const propertyName = 'a';
+    const currentOutput = contains(input, propertyName);
+    const targetOutput = true;
+
+    expect(currentOutput).toEqual(targetOutput);
+});
+
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
 
+test("given an object does not contain a property name, returns false", function (){
+    const input = {a: 1, b: 2};
+    const propertyName = 'c';
+    const currentOutput = contains(input, propertyName);
+    const targetOutput = false;
+
+    expect(currentOutput).toEqual(targetOutput);
+});
+
 // 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", function (){
+    const input = [1, 2, 3];
+    const propertyName = 'a';
+    const currentOutput = contains(input, propertyName);
+    const targetOutput = false;
+
+    expect(currentOutput).toEqual(targetOutput);
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,11 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  const lookup = {};
+
+  for (const [country, currency] of pairs) {
+    lookup[country] = currency;
+  }
+
+  return lookup;
 }
 
-module.exports = createLookup;
+module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,7 +1,20 @@
 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 input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+    ["GB", "GBP"],
+  ];
+
+  const result = createLookup(input);
+
+  expect(result).toEqual({
+    US: "USD",
+    CA: "CAD",
+    GB: "GBP",
+  });
+});
 /*
 
 Create a lookup object of key value pairs from an array of code pairs

Sprint-2/implement/querystring.js

@@ -1,12 +1,33 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
+
+  if (!queryString) {
     return queryParams;
   }
+
+  if (queryString.startsWith("?")) {
+    queryString = queryString.slice(1);
+  }
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    if (!pair) continue;
+
+    const firstEq = pair.indexOf("=");
+
+    let key;
+    let value;
+
+    if (firstEq === -1) {
+
+      key = pair;
+      value = "";
+    } else {
+      key = pair.slice(0, firstEq);
+      value = pair.slice(firstEq + 1);
+    }
+
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -10,3 +10,31 @@ test("parses querystring values containing =", () => {
     "equation": "x=y+1",
   });
 });
+
+test("parses multiple key=value pairs", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({ a: "1", b: "2" });
+});
+
+test("handles empty value (a=)", () => {
+  expect(parseQueryString("a=")).toEqual({ a: "" });
+});
+
+test("handles key with no '=' (a)", () => {
+  expect(parseQueryString("a")).toEqual({ a: "" });
+});
+
+test("last value wins for repeated keys", () => {
+  expect(parseQueryString("a=1&a=2")).toEqual({ a: "2" });
+});
+
+test("supports leading question mark", () => {
+  expect(parseQueryString("?a=1&b=2")).toEqual({ a: "1", b: "2" });
+});
+
+test("ignores empty pairs from trailing or consecutive &", () => {
+  expect(parseQueryString("a=1&&b=2&")).toEqual({ a: "1", b: "2" });
+});
+
+test("handles empty key (=value) producing empty-string key", () => {
+  expect(parseQueryString("=value")).toEqual({ "": "value" });
+});

Sprint-2/implement/tally.js

@@ -1,3 +1,19 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("tally expects an array");
+  }
+
+  const counts = {};
+
+  for (const item of items) {
+    if (counts[item] === undefined) {
+      counts[item] = 1;
+    } else {
+      counts[item] += 1;
+    }
+  }
+
+  return counts;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -19,16 +19,37 @@ 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 returns counts for each unique item", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({
+    a: 2,
+    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 counts each unique item", () => {
+  expect(tally(["a", "a", "b", "c", "a"])).toEqual({
+    a: 3,
+    b: 1,
+    c: 1,
+  });
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("tally throws an error when given a non-array", () => {
+  expect(() => tally("not an array")).toThrow();
+  expect(() => tally(123)).toThrow();
+  expect(() => tally({})).toThrow();
+});

Sprint-2/interpret/invert.js

@@ -16,14 +16,52 @@ function invert(obj) {
   return invertedObj;
 }
 
-// a) What is the current return value when invert is called with { a : 1 }
+// 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 }
+// 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}
+// 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?
+// c) What does Object.entries return? Why is it needed in this program? >> Object.entries returns an array of key-value paris.
 
-// d) Explain why the current return value is different from the target output
+// d) Explain why the current return value is different from the target output >> Because invertedObj.key = value creates a property called (key) instead of using hte variable key.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+// The fixed code:
+function invert(obj) {
+  const invertedObj = {};
+
+  for (const [key, value] of Object.entries(obj)) {
+    invertedObj[value] = key;
+  }
+
+  return invertedObj;
+}
+
+module.exports = invert;
+
+// Tests:
+const invert = require("./invert.js");
+
+// Single key
+test("invert works for one key-value pair", () => {
+  expect(invert({ a: 1 })).toEqual({ "1": "a" });
+});
+
+// Multiple keys
+test("invert swaps keys and values for multiple pairs", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({
+    "1": "a",
+    "2": "b",
+  });
+});
+
+// Empty object
+test("invert of an empty object returns empty", () => {
+  expect(invert({})).toEqual({});
+});
+
+// Values become string keys
+test("invert always returns string keys", () => {
+  expect(invert({ x: 10 })).toEqual({ "10": "x" });
+});