London | 26-ITP-Sep | Mandip Sanger | Sprint 2 | Coursework

Sprint-2/debug/address.js

@@ -12,4 +12,4 @@ 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

@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const key in author) {
+  console.log(author[key]);
 }

Sprint-2/debug/recipe.js

@@ -12,4 +12,4 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join("\n")}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,19 @@
-function contains() {}
+function contains(object, property) {
+  if (typeof object !== "object" || object === null || Array.isArray(object)) {
+    throw new Error("contains requires an object");
+  }
+
+  return Object.prototype.hasOwnProperty.call(object, property);
+}
 
 module.exports = contains;
+
+// Implement a function called contains that checks an object contains a
+// particular property
+
+// E.g. contains({a: 1, b: 2}, 'a') // returns true
+// as the object contains a key of 'a'
+
+// E.g. contains({a: 1, b: 2}, 'c') // returns false
+// as the object doesn't contains a key of 'c'
+// */

Sprint-2/implement/contains.test.js

@@ -1,40 +1,74 @@
 const contains = require("./contains.js");
 
-/*
-Implement a function called contains that checks an object contains a
-particular property
-
-E.g. contains({a: 1, b: 2}, 'a') // returns true
-as the object contains a key of 'a'
-
-E.g. contains({a: 1, b: 2}, 'c') // returns false
-as the object doesn't contains a key of 'c'
-
-E.g. contains([1, 2, 3], 'a') throws Error("contains requires an object")
-as an array isn't an object
-*/
-
-// 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");
+test("returns false for an empty object", () => {
+  const currentOutput = contains({});
+  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("returns true when the property exists", () => {
+  const currentOutput = contains({ a: 1, b: 2 }, "a");
+  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("returns false when the property does not exist", () => {
+  const currentOutput = contains({ a: 1, b: 2 }, "c");
+  const targetOutput = false;
+
+  expect(currentOutput).toEqual(targetOutput);
+});
+
+// Given an array
+// When passed to contains
+// Then it should throw an error
+test("throws an error when passed an array", () => {
+  expect(() => contains([1, 2, 3], "a")).toThrow(
+    new Error("contains requires an object")
+  );
+});
+
+// Given a string
+// When passed to contains
+// Then it should throw an error
+test("throws an error when passed a string", () => {
+  expect(() => contains("hello", "a")).toThrow(
+    new Error("contains requires an object")
+  );
+});
+
+// Given a number
+// When passed to contains
+// Then it should throw an error
+test("throws an error when passed a number", () => {
+  expect(() => contains(42, "a")).toThrow(
+    new Error("contains requires an object")
+  );
+});
+
+// Given null
+// When passed to contains
+// Then it should throw an error
+test("throws an error when passed null", () => {
+  expect(() => contains(null, "a")).toThrow(
+    new Error("contains requires an object")
+  );
+});
 
-// Given a value that isn't an object - an array, a string, a number,
-// null, or no argument at all
+// Given no argument
 // When passed to contains
-// Then it should throw Error("contains requires an object")
-// (careful: typeof [] and typeof null are both "object")
+// Then it should throw an error
+test("throws an error when passed no argument", () => {
+  expect(() => contains()).toThrow(new Error("contains requires an object"));
+});

Sprint-2/implement/querystring.js

@@ -3,10 +3,24 @@ function parseQueryString(queryString) {
   if (queryString.length === 0) {
     return queryParams;
   }
-  const keyValuePairs = queryString.split("&");
+  const keyValuePairs = queryString.split("&").filter((pair) => pair !== "");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const indexFirstEqual = pair.indexOf("=");
+
+    let key;
+    let value;
+
+    if (indexFirstEqual === -1) {
+      key = pair;
+      value = "";
+    } else {
+      key = pair.slice(0, indexFirstEqual);
+      value = pair.slice(indexFirstEqual + 1);
+    }
+    key = decodeURIComponent(key.replace(/\+/g, " "));
+    value = decodeURIComponent(value.replace(/\+/g, " "));
+
     queryParams[key] = value;
   }
 

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({
@@ -12,17 +12,30 @@ test("should parse values containing '='", () => {
 });
 
 test("should ignore empty key-value pairs", () => {
-  expect(parseQueryString("key1=value1&&key2=value2&")).toEqual({
+  const input = "key1=value1&&key2=value2&";
+
+  const currentOutput = parseQueryString(input);
+
+  const targetOutput = {
     key1: "value1",
     key2: "value2",
-  });
+  };
+
+  expect(currentOutput).toEqual(targetOutput);
 });
 
 test("should accept empty string as key or as value", () => {
-  expect(parseQueryString("=value")).toEqual({ "": "value" });
-  expect(parseQueryString("key")).toEqual({ key: "" });
-  expect(parseQueryString("key=")).toEqual({ key: "" });
-  expect(parseQueryString("=")).toEqual({ "": "" });
+  expect(parseQueryString("=value")).toEqual({
+    "": "value",
+  });
+
+  expect(parseQueryString("key=")).toEqual({
+    key: "",
+  });
+
+  expect(parseQueryString("=")).toEqual({
+    "": "",
+  });
 });
 
 test("should decode percent-encoded characters", () => {
@@ -32,17 +45,29 @@ test("should decode percent-encoded characters", () => {
 });
 
 test("should replace '+' by ' '", () => {
-  expect(parseQueryString("full+name=John+Doe")).toEqual({
+  const input = "full+name=John+Doe";
+
+  const currentOutput = parseQueryString(input);
+
+  const expectedOutput = {
     "full name": "John Doe",
-  });
+  };
+
+  expect(currentOutput).toEqual(expectedOutput);
 });
 
 // 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",
-  });
-});
+// test("should store values of a key in an array when the key has 2 or more values", () => {
+//   const input = "key=value1&key=value2&key=value3&foo=bar";
+
+//   const currentOutput = parseQueryString(input);
+
+//   const expectedOutput = {
+//     key: ["value1", "value2", "value3"],
+//     foo: "bar",
+//   };
+
+//   expect(currentOutput).toEqual(expectedOutput);
+// });

Sprint-2/implement/tally.js

@@ -1,3 +1,33 @@
-function tally() {}
+function tally(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("tally requires an array");
+  }
+
+  const result = {};
+
+  for (const item of list) {
+    if (Object.hasOwn(result, item)) {
+      result[item]++;
+    } else {
+      result[item] = 1;
+    }
+  }
+
+  return result;
+}
 
 module.exports = tally;
+
+/**
+ * tally array
+ *
+ * In this task, you'll need to implement a function called tally
+ * that will take a list of items and count the frequency of each item
+ * in an array
+ *
+ * For example:
+ *
+ * tally(['a']), target output: { a: 1 }
+ * tally(['a', 'a', 'a']), target output: { a: 3 }
+ * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
+ */

Sprint-2/implement/tally.test.js

@@ -11,24 +11,53 @@ const tally = require("./tally.js");
  *
  * tally(['a']), target output: { a: 1 }
  * tally(['a', 'a', 'a']), target output: { a: 3 }
- * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
+ * tally(['a', 'a', 'b', 'c']), target output: { a: 2, b: 1, c: 1 }
  */
 
-// Acceptance criteria:
-
 // 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 the count for one item", () => {
+  expect(tally(["a"])).toEqual({
+    a: 1,
+  });
+});
+
+test("returns the correct count for duplicate items", () => {
+  expect(tally(["a", "a", "a"])).toEqual({
+    a: 3,
+  });
+});
+
+test("returns the correct count for multiple unique items", () => {
+  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");
 
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
+test("returns an empty object when given an empty array", () => {
+  expect(tally([])).toEqual({});
+});
 
 // 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 given a string", () => {
+  expect(() => tally("hello")).toThrow(new Error("tally requires an array"));
+});
+
+test("throws an error when given a number", () => {
+  expect(() => tally(42)).toThrow(new Error("tally requires an array"));
+});
+
+test("throws an error when given no argument", () => {
+  expect(() => tally()).toThrow(new Error("tally requires an array"));
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,36 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+module.exports = invert;
+
 // 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?
+//
+//[
+// ["a", 1],
+//["b", 2]
+//]
 
 // d) Explain why the current return value is different from the target output
+//invertedObj.key = value; means "create a property named key".
+//It does not mean "use the variable key as the property name."
+//invertedObj[value] = key; Square brackets allow the variable's value to become the property name.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)