stretch

Author: ihortar

Sprint-2/stretch/count-words.js

@@ -1,28 +1,55 @@
 /*
   Count the number of times a word appears in a given string.
 
+
   Write a function called countWords that
     - takes a string as an argument
     - returns an object where
           - the keys are the words from the string and
           - the values are the number of times the word appears in the string
 
+
   Example
   If we call countWords like this:
 
+
   countWords("you and me and you") then the target output is { you: 2, and: 2, me: 1 }
 
+
   To complete this exercise you should understand
     - Strings and string manipulation
     - Loops
     - Comparison inside if statements
     - Setting values on an object
 
+
 ## Advanced challenges
 
+
 1. Remove all of the punctuation (e.g. ".", ",", "!", "?") to tidy up the results
 
+
 2. Ignore the case of the words to find more unique words. e.g. (A === a, Hello === hello)
 
+
 3. Order the results to find out which word is the most common in the input
 */
+
+
+
+function countWords(str) {
+  const counts = {};
+
+  const words = str.split(" ").filter((w) => w !== "");
+
+  for (const word of words) {
+    if (counts[word]) {
+      counts[word] += 1;
+    } else {
+      counts[word] = 1;
+    }
+  }
+
+  return counts;
+}
+

Sprint-2/stretch/mode.js

@@ -1,29 +1,36 @@
 // You are given an implementation of calculateMode
 
+
 // calculateMode's implementation can be broken down into two stages:
 
+
 // Stage 1. One part of the code tracks the frequency of each value
 // Stage 2. The other part finds the value with the highest frequency
 
+
 // refactor calculateMode by splitting up the code
 // into smaller functions using the stages above
 
-function calculateMode(list) {
-  // track frequency of each value
-  let freqs = new Map();
 
-  for (let num of list) {
+function getFrequencies(list) {
+  const freqs = new Map();
+
+  for (const num of list) {
     if (typeof num !== "number") {
       continue;
     }
 
     freqs.set(num, (freqs.get(num) || 0) + 1);
   }
 
-  // Find the value with the highest frequency
+  return freqs;
+}
+
+function getModeFromFrequencies(freqs) {
   let maxFreq = 0;
   let mode;
-  for (let [num, freq] of freqs) {
+
+  for (const [num, freq] of freqs) {
     if (freq > maxFreq) {
       mode = num;
       maxFreq = freq;
@@ -33,4 +40,9 @@ function calculateMode(list) {
   return maxFreq === 0 ? NaN : mode;
 }
 
+function calculateMode(list) {
+  const freqs = getFrequencies(list);
+  return getModeFromFrequencies(freqs);
+}
+
 module.exports = calculateMode;

Sprint-2/stretch/mode.test.js

@@ -1,16 +1,20 @@
 const calculateMode = require("./mode.js");
 
+
 // Acceptance criteria for calculateMode function
 
+
 // Given an array of numbers
 // When calculateMode is called on the array
 // Then it should return the number that appears most frequently in the array
 
+
 // Example:
 // Given [2,4,1,2,3,2,1]
 // When calculateMode is called on [2,4,1,2,3,2,1]
 // Then it should return 2 */
 
+
 describe("calculateMode()", () => {
   test("returns the most frequent number in an array", () => {
     const nums = [2, 4, 1, 2, 3, 2, 1];

Sprint-2/stretch/till.js

@@ -1,19 +1,23 @@
 // totalTill takes an object representing coins in a till
 
+
 // Given an object of coins
 // When this till object is passed to totalTill
 // Then it should return the total amount in pounds
 
+
 function totalTill(till) {
   let total = 0;
 
   for (const [coin, quantity] of Object.entries(till)) {
-    total += coin * quantity;
+    const valueInPence = Number(coin.replace("p", ""));
+    total += valueInPence * quantity;
   }
 
   return `£${total / 100}`;
 }
 
+
 const till = {
   "1p": 10,
   "5p": 6,
@@ -22,10 +26,17 @@ const till = {
 };
 const totalAmount = totalTill(till);
 
+
 // a) What is the target output when totalTill is called with the till object
+// "£4.4"
+
 
 // b) Why do we need to use Object.entries inside the for...of loop in this function?
+// Object.entries returns [coin, quantity] pairs, allowing destructuring in the loop
+
 
 // c) What does coin * quantity evaluate to inside the for...of loop?
+// Original: "1p" * 10 = NaN. Fixed: 1 * 10 = 10 (pence for that coin type)
+
 
-// d) Write a test for this function to check it works and then fix the implementation of totalTill
+module.exports = totalTill;

Sprint-2/stretch/totalTill.test.js

@@ -0,0 +1,6 @@
+const totalTill = require("./totalTill.js");
+
+test("calculates total till value in pounds", () => {
+  const till = { "1p": 10, "5p": 6, "50p": 4, "20p": 10 };
+  expect(totalTill(till)).toBe("£4.4");
+});