London | 26-ITP-Jan | Abdul Moiz | Sprint 2 | Data Groups

Sprint-2/debug/address.js

@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+// Prediction: Error is that address is not an array, so address[0] is undefined.
+// Actual output: "My house number is undefined"
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that 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

@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+// Prediction: The error is that it is trying to iterate over a non-array object.
+// Actual output: TypeError: author is not iterable
+
 // 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 +14,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
+for (const key in author) {
+  console.log(key + ": " + author[key]);
 }

Sprint-2/debug/recipe.js

@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+// Prediction: The error is that recipe is being treated as a string
+// Actual output: bruschetta serves 2 [object Object]
+
 // 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?
@@ -11,5 +14,5 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:
+${recipe.ingredients.join(", ")}`);

Sprint-2/implement/contains.js

@@ -1,3 +1,15 @@
-function contains() {}
+function contains(object, name) {
+  if (object == null || Object.keys(object).length === 0) {
+    return false;
+  }
+
+  for (let key in object) {
+    if (key === name) {
+      return true;
+    }
+  }
+
+  return false;
+}
 
 module.exports = contains;

Sprint-2/implement/contains.test.js

@@ -20,7 +20,6 @@ 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");
 
 // Given an object with properties
 // When passed to contains with an existing property name
@@ -33,3 +32,15 @@ test.todo("contains on empty object returns false");
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+
+describe("contains", () => {
+  [
+    { input: [{}, "a"], expected: false },
+    { input: [{ a: 1, b: 2 }, "a"], expected: true },
+    { input: [{ a: 1, b: 2 }, "c"], expected: false },
+    { input: [null, "a"], expected: false },
+  ].forEach(({ input, expected }) =>
+    it(`return if object contains the key for ${input[1]}`, () =>
+      expect(contains(...input)).toEqual(expected))
+  );
+});

Sprint-2/implement/lookup.js

@@ -1,5 +1,13 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  const array = {};
+
+  for (const pair of countryCurrencyPairs) {
+    const country = pair[0];
+    const currency = pair[1];
+    array[country] = currency;
+  }
+
+  return array;
 }
 
 module.exports = createLookup;

Sprint-2/implement/querystring.js

@@ -6,7 +6,8 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const [key, ...rest] = pair.split("=");
+    const value = rest.join("=");
     queryParams[key] = value;
   }
 

Sprint-2/implement/querystring.test.js

@@ -3,10 +3,23 @@
 // Below is one test case for an edge case the implementation doesn't handle well.
 // Fix the implementation for this test, 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("parses querystring values containing =", () => {
-  expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+describe("parseQueryString", () => {
+  test("returns an empty object when query is empty", () => {
+    expect(parseQueryString("")).toEqual({});
+  });
+
+  test("parses query string values containing =", () => {
+    expect(parseQueryString("equation=x=y+1")).toEqual({
+      equation: "x=y+1",
+    });
+  });
+
+  test("checks for keys without values", () => {
+    expect(parseQueryString("foo&bar=2")).toEqual({
+      foo: "",
+      bar: "2",
+    });
   });
 });

Sprint-2/implement/tally.js

@@ -1,3 +1,19 @@
-function tally() {}
+function tally(itemsList) {
+  const counts = {};
+
+  if (itemsList.length === 0) {
+    return {};
+  }
+
+  if (!Array.isArray(itemsList)) {
+    throw new Error("Input must be an array");
+  }
+
+  for (const item of itemsList) {
+    counts[item] = (counts[item] || 0) + 1;
+  }
+
+  return counts;
+}
 
 module.exports = tally;

Sprint-2/implement/tally.test.js

@@ -32,3 +32,21 @@ test.todo("tally on an empty array returns an empty object");
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+
+describe("tally", () => {
+  test("returns an empty object when given an empty array", () => {
+    expect(tally([])).toEqual({});
+  });
+
+  test("returns counts for each unique item", () => {
+    expect(tally(["a", "a", "b", "c"])).toEqual({
+      a: 2,
+      b: 1,
+      c: 1,
+    });
+  });
+
+  test("throws an error when input is not an array", () => {
+    expect(() => tally("abc")).toThrow();
+  });
+});

Sprint-2/interpret/invert.js

@@ -10,20 +10,28 @@ 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?
+// Object.entries returns an array of the key value pairs in an object
+// It is needed because without it, iterating over the object is not possible
 
 // d) Explain why the current return value is different from the target output
+// InvertedObj.key creates a key called 'key' in the object
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,23 @@
+const invert = require("./invert");
+
+describe("invert", () => {
+  test("object with numbers as values", () => {
+    expect(invert({ a: 1, b: 2 })).toEqual({ 1: "a", 2: "b" });
+  });
+
+  test("1 pair in object", () => {
+    expect(invert({ x: 99 })).toEqual({ 99: "x" });
+  });
+
+  test("number keys with string values", () => {
+    expect(invert({ 1: "one", 2: "two" })).toEqual({ one: "1", two: "2" });
+  });
+
+  test("empty object returns empty object", () => {
+    expect(invert({})).toEqual({});
+  });
+
+  test("mixed types", () => {
+    expect(invert({ a: 1, b: "hello" })).toEqual({ 1: "a", hello: "b" });
+  });
+});