Manchester | 26-ITP-Sept | Aklilu Mihtsun | Sprint 2 | Coursework/sprint 2

Sprint-2/debug/address.js

@@ -1,5 +1,9 @@
 // Predict and explain first...
 
+// I predict that the code will give undefined result, because objects access properties using the key names not indexes
+// And the square bracket will generate a reference error because the houseNumber will be treated
+//  as a variable name not property key
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +16,4 @@ 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

@@ -1,8 +1,14 @@
 // Predict and explain first...
 
+// I predict the code will generate error, because it has used for of loop which is for looping array,
+//  instead of for in loop that is for looping objects
+
 // 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
 
+// when we run it, it logs out the property key instead of its value because for...in iterates over the property keys (names), not the property values.
+// we need to use square brackets [] to access the value associated with that property name
+
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +17,6 @@ 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

@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+// I predict the code will not print the ingredients, because the array is not referenced,
+// and it does not have loop to go through each element of the array
+
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
 // How can you fix it?
@@ -9,7 +12,6 @@ const recipe = {
   serves: 2,
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
-
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+console.log(
+  recipe.title + " serves " + recipe.serves + recipe.ingredients.join("\n")
+);

Sprint-2/implement/contains.js

@@ -1,3 +1,9 @@
-function contains() {}
-
+function contains(object, name) {
+  if (typeof object !== "object" || Array.isArray(object) || object === null) {
+    throw new Error("contains requires an object");
+  }
+  // the in Checks own and inherited properties so that is why it returned true when the name is 'toString'
+  return Object.hasOwn(object, name);
+}
+//console.log(contains({ a: 1 }, "toString"));
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -23,18 +23,52 @@ as an array isn't an object
 // 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({}, "a")).toBe(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("contains name on object returns true", () => {
+  expect(contains({ a: 1, b: 2, c: 3 }, "a")).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("contains name not on object returns false", () => {
+  expect(contains({ a: 1, b: 2, c: 3 }, "e")).toBe(false);
+});
 
 // Given a value that isn't an object - an array, a string, a number,
 // null, or no argument at all
 // When passed to contains
 // Then it should throw Error("contains requires an object")
 // (careful: typeof [] and typeof null are both "object")
+
+describe("when the argument is not an object", () => {
+  test("throws an error when receiving a string", () => {
+    expect(() => {
+      contains("Hello World", "e");
+    }).toThrow("contains requires an object");
+  });
+
+  test("throws an error when receiving a number", () => {
+    expect(() => {
+      contains(1234, "a");
+    }).toThrow("contains requires an object");
+  });
+
+  test("throws an error when receiving an array", () => {
+    expect(() => {
+      contains(["a", "b", "c"], "a");
+    }).toThrow("contains requires an object");
+  });
+
+  test("throws an error when receiving null", () => {
+    expect(() => {
+      contains(null, "a");
+    }).toThrow("contains requires an object");
+  });
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,22 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  if (!Array.isArray(countryCurrencyPairs)) {
+    throw new Error("createLookup requires an array");
+  }
+  for (const keyVlauePairs of countryCurrencyPairs) {
+    if (!Array.isArray(keyVlauePairs)) {
+      throw new Error("createLookup requires an array of key value pair");
+    } else if (keyVlauePairs.length !== 2) {
+      throw new Error("createLookup requires key value pair");
+    } else if (keyVlauePairs.some((element) => typeof element !== "string")) {
+      throw new Error("createLookup requires a string of key value pair");
+    }
+  }
+
+  let currencyObject = {};
+  for (const arrayCurrency of countryCurrencyPairs) {
+    currencyObject[arrayCurrency[0]] = arrayCurrency[1];
+  }
+  return currencyObject;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,37 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("returns an object of country currency pair", () => {
+  expect(
+    createLookup([
+      ["US", "USD"],
+      ["CA", "CAD"],
+    ])
+  ).toEqual({ US: "USD", CA: "CAD" });
+});
+
+test("Throws an error when there are more strings than key value pairs", () => {
+  expect(() => {
+    createLookup([
+      ["US", "USD", "EURO"],
+      ["CA", "CAD"],
+    ]);
+  }).toThrow("createLookup requires key value pair");
+});
+
+test("Throws an error if the input is not an array", () => {
+  expect(() => {
+    createLookup(["usd", "cad", "euro"]);
+  }).toThrow("createLookup requires an array");
+});
+
+test("Throws an error if an array has elements that are not string key value pairs", () => {
+  expect(() => {
+    createLookup([
+      [23, "USD"],
+      ["CA", 67],
+    ]);
+  }).toThrow("createLookup requires a string of key value pair");
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -3,11 +3,40 @@ function parseQueryString(queryString) {
   if (queryString.length === 0) {
     return queryParams;
   }
+  if (queryString.includes("%")) {
+    queryString = decodeURIComponent(queryString);
+  }
+  if (queryString.includes("+")) {
+    queryString = queryString.replaceAll("+", " ");
+  }
+  //const arrayValue = [];
+  let key = "";
+  let value = "";
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (pair.length === 0) {
+      continue;
+    }
+    const separatorIndex = pair.indexOf("=");
+    if (separatorIndex === 0) {
+      value = pair.slice(separatorIndex + 1);
+    } else if (separatorIndex === pair.length - 1) {
+      key = pair.slice(0, separatorIndex);
+    } else if (!pair.includes("=")) {
+      key = pair;
+    } else {
+      key = pair.slice(0, separatorIndex);
+      value = pair.slice(separatorIndex + 1);
+    }
+    if (!queryParams[key]) {
+      queryParams[key] = value;
+    } else if (Array.isArray(queryParams[key])) {
+      queryParams[key].push(value);
+    } else {
+      queryParams[key] = [queryParams[key], value];
+    }
   }
 
   return queryParams;

Sprint-2/implement/querystring.test.js

@@ -3,7 +3,7 @@
 // Below are some test cases the implementation doesn't handle well.
 // Fix the implementation for these tests, and try to think of as many other edge cases as possible - write tests and fix those too.
 
-const parseQueryString = require("./querystring.js")
+const parseQueryString = require("./querystring.js");
 
 test("should parse values containing '='", () => {
   expect(parseQueryString("equation=a=b-2")).toEqual({

Sprint-2/implement/tally.js

@@ -1,3 +1,16 @@
-function tally() {}
+function tally(array) {
+  if (!Array.isArray(array)) {
+    throw new Error("tally requires an array");
+  }
+  const objectItem = {};
+  for (const item of array) {
+    if (objectItem[item]) {
+      objectItem[item] = objectItem[item] + 1;
+    } else {
+      objectItem[item] = 1;
+    }
+  }
+  return objectItem;
+}
 
 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("returns count for each unique item in the array", () => {
+  expect(tally(["a", "b", "b", "a", "c"])).toEqual({ a: 2, b: 2, 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("returns empty object for given empty array", () => {
+  expect(tally([])).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("returns count for each unique item with different type in the array", () => {
+  expect(tally(["a", "b", 3, "a", "c"])).toEqual({ a: 2, b: 1, 3: 1, c: 1 });
+});
 
 // Given an invalid input like a string, a number, or no argument at all
 // When passed to tally
 // Then it should throw Error("tally requires an array")
+test("throws an error when not given an array", () => {
+  expect(() => {
+    tally("apple");
+  }).toThrow("tally requires an array");
+
+  expect(() => {
+    tally(234);
+  }).toThrow("tally requires an array");
+
+  expect(() => {
+    tally();
+  }).toThrow("tally requires an array");
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,35 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
+//console.log(invert({ f: 34, h: 45, j: "rf" }));
+module.exports = invert;
 
 // 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 }
+
 // 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 return the key and value of an object, and in this program we used it to go through each key value pair and to put them in an array
+
 // d) Explain why the current return value is different from the target output
 
+// ===> first it used the dot notation instead of square bracket which is accessing the property using  a literal name
+// ===> second it is not inverted it still uses key value instead of value key so that it returns the inverted one
+
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+// ===> I have fixed the program

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,10 @@
+const invert = require("./invert.js");
+
+test("checking inversion ", () => {
+  expect(invert({ x: 10, y: 20 })).toEqual({ 10: "x", 20: "y" });
+  expect(invert({ f: 34, h: 45, j: "rf" })).toEqual({
+    34: "f",
+    45: "h",
+    rf: "j",
+  });
+});

Sprint-2/jsconfig.json

@@ -0,0 +1,6 @@
+{
+  "compilerOptions": {
+    "types": ["jest"]
+  },
+  "exclude": ["node_modules"]
+}