London | 26-ITP-May | Alex Jamshidi | Sprint 2 | Exercises

Sprint-2/debug/address.js

@@ -1,4 +1,5 @@
 // Predict and explain first...
+// This will fail because to parse from an object requires a key, not an index value
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +13,6 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(
+  `My house number is ${address.houseNumber}, ${address.street}, ${address.city}, ${address.country}, ${address.postcode}`
+);

Sprint-2/debug/author.js

@@ -1,4 +1,5 @@
 // Predict and explain first...
+// the for loop it the syntax for an array, I'm not sure it will work with an object
 
 // 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 +12,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }

Sprint-2/debug/recipe.js

@@ -1,4 +1,6 @@
 // Predict and explain first...
+// the title and serves looks like it would work, the ingredients list is just calling the recipe object
+// that won't list any values and may return an error or undefined.
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -11,5 +13,5 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:
+${recipe.ingredients.join("\n")}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,12 @@
-function contains() {}
+function contains(object, property) {
+  if (typeof object !== "object" || !object || Array.isArray(object)) {
+    return false;
+  }
+  if (typeof property !== "string" || !object) {
+    return false;
+  }
+
+  return Object.hasOwn(object, property);
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -12,24 +12,51 @@ as the object doesn't contains a key of 'c'
 */
 
 // Acceptance criteria:
-
 // 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
 
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+describe("contains", () => {
+  // Given an empty object
+  // When passed to contains
+  // Then it should return false
+  it("contains on empty object returns false", () => {
+    const object = {};
+    const property = "a";
+    expect(contains(object, property)).toEqual(false);
+  });
+
+  // Given an object with properties
+  // When passed to contains with an existing property name
+  // Then it should return true
+  it("object contains property returns true", () => {
+    const object = { a: 1, b: 2 };
+    const property = "a";
+    expect(contains(object, property)).toEqual(true);
+  });
+
+  // Given an object with properties
+  // When passed to contains with a non-existent property name
+  // Then it should return false
+  it("object does not contain property returns false", () => {
+    const object = { a: 1, b: 2 };
+    const property = "c";
+    expect(contains(object, property)).toEqual(false);
+  });
+
+  // Given invalid parameters like an array
+  // When passed to contains
+  // Then it should return false or throw an error
+  it("given invalid parameter (an array) returns false or throws an error", () => {
+    expect(contains([], [])).toEqual(false);
+    expect(contains(["a", 1], "a")).toEqual(false);
+    expect(contains({ a: 1, b: 2 }, ["a"])).toEqual(false);
+    expect(contains(["a", 1], ["a"])).toEqual(false);
+  });
+
+  it("given null returns false", () => {
+    expect(contains(null, "a")).toEqual(false);
+    expect(contains({ a: 1, b: 2 }, null)).toEqual(false);
+    expect(contains(null, null)).toEqual(false);
+  });
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,9 @@
-function createLookup() {
-  // implementation here
+function createLookup(arrayOfArrays) {
+  const lookup = {};
+  for (const array of arrayOfArrays) {
+    lookup[array[0]] = array[1];
+  }
+  return lookup;
 }
 
 module.exports = createLookup;

Sprint-2/implement/lookup.test.js

@@ -1,6 +1,19 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+describe("createLookup", () => {
+  it("creates a country currency code lookup for multiple codes", () => {
+    const arrayOfArrays = [
+      ["US", "USD"],
+      ["CA", "CAD"],
+      ["UK", "GBP"],
+    ];
+    expect(createLookup(arrayOfArrays)).toEqual({
+      US: "USD",
+      CA: "CAD",
+      UK: "GBP",
+    });
+  });
+});
 
 /*
 

Sprint-2/implement/querystring.js

@@ -3,11 +3,24 @@ function parseQueryString(queryString) {
   if (queryString.length === 0) {
     return queryParams;
   }
+
+  // Adds percentage-encoded characters
+  queryString = decodeURIComponent(queryString);
+
+  // Replaces + with space
+  queryString = queryString.replaceAll("+", " ");
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (pair !== "") {
+      let index = pair.indexOf("=");
+      if (!pair.includes("=")) {
+        index = pair.length;
+      }
+      const [key, value] = [pair.slice(0, index), pair.slice(index + 1)];
+      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({
@@ -40,9 +40,11 @@ test("should replace '+' by ' '", () => {
 // Stretch exercise: Handling query strings that contain identical keys
 
 // Delete this test if you are not working on this optional case
+/*
 test("should store values of a key in an array when the key has 2 or more values", () => {
   expect(parseQueryString("key=value1&key=value2&key=value3&foo=bar")).toEqual({
     key: ["value1", "value2", "value3"],
     foo: "bar",
   });
 });
+*/

Sprint-2/implement/tally.js

@@ -1,3 +1,14 @@
-function tally() {}
+function tally(array) {
+  if (!Array.isArray(array)) {
+    throw new Error("Invalid array");
+  }
+  const count = Object.create(null);
+  array.forEach((item) => {
+    if (item in count) {
+      count[item] += 1;
+    } else count[item] = 1;
+  });
+  return count;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -20,15 +20,30 @@ const tally = require("./tally.js");
 // When passed an array of items
 // Then it should return an object containing the count for each unique item
 
-// 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");
+describe("tally", () => {
+  // Given an empty array
+  // When passed to tally
+  // Then it should return an empty object
+  it("tally on an empty array returns an empty object", () => {
+    const array = [];
+    expect(tally(array)).toEqual({});
+  });
 
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
+  // Given an array with duplicate items
+  // When passed to tally
+  // Then it should return counts for each unique item
+  it("tally returns counts for each unique item", () => {
+    expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+    expect(tally(["toString", "toString"])).toEqual({ toString: 2 });
+  });
 
-// Given an invalid input like a string
-// When passed to tally
-// Then it should throw an error
+  // Given an invalid input like a string
+  // When passed to tally
+  // Then it should throw an error
+  it("tally on an empty array returns an empty object", () => {
+    const array = "string";
+    expect(() => {
+      tally(array);
+    }).toThrow("Invalid array");
+  });
+});

Sprint-2/interpret/invert.js

@@ -6,24 +6,35 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
+invert({ a: 1, b: 2 });
+
 function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
-
+  console.log(invertedObj);
   return invertedObj;
 }
 
 // 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?
+// It turns the object into an array of arrays
+// It's needed so the for..of loop can access the key:value pairs
 
 // d) Explain why the current return value is different from the target output
+// invertedObj.key = value;
+// this line of code sets the key to "key"
+// even if that worked as intended, the key and value haven't been swapped
 
 // 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 +1,13 @@
+const invert = require("./invert.js");
+
+describe("invert", () => {
+  it("object returns inverted object", () => {
+    // a) What is the current return value when invert is called with { a : 1 }
+    let object = { a: 1 };
+    expect(invert(object)).toEqual({ 1: "a" });
+
+    // b) What is the current return value when invert is called with { a: 1, b: 2 }
+    object = { a: 1, b: 2 };
+    expect(invert(object)).toEqual({ 1: "a", 2: "b" });
+  });
+});