London | May 2025 | Houssam Lahlah | Acoursework/sprint 2

Sprint-2/1-key-errors/0.js

@@ -1,5 +1,7 @@
 // Predict and explain first...
-//  =============> write your prediction here
+//  =============> // =============> write your prediction here
+//  I predict the code will throw an error because the variable `str` is being declared twice in the same function scope.
+
 
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
@@ -9,5 +11,17 @@ function capitalise(str) {
   return str;
 }
 
-// =============> write your explanation here
+// =============>  write your explanation here
+// The function already receives `str` as a parameter. 
+// Inside the function, it tries to declare `let str = ...`, 
+// which causes a conflict because JavaScript does not 
+// allow redeclaring the same variable name in the same scope using `let`. 
+// This leads to a `SyntaxError: Identifier 'str' has already been declared`.
+
+
 // =============> write your new code here
+// =============> write your new code here
+function capitalise(str) {
+  let capitalisedStr = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return capitalisedStr;
+}

Sprint-2/1-key-errors/1.js

@@ -1,4 +1,9 @@
 // Predict and explain first...
+// =============> write your prediction here
+//   I predict this program will throw a `SyntaxError` because 
+// the parameter `decimalNumber` is being redeclared inside the function using `const`. 
+// Also, the variable `decimalNumber` is being accessed outside the function where it's not defined.
+
 
 // Why will an error occur when this program runs?
 // =============> write your prediction here
@@ -15,6 +20,20 @@ function convertToPercentage(decimalNumber) {
 console.log(decimalNumber);
 
 // =============> write your explanation here
+// The function already has a parameter named `decimalNumber`, 
+// but inside the function, it's trying to declare another 
+// constant with the same name: `const decimalNumber = 0.5;`. 
+// JavaScript doesn’t allow redeclaring a variable that already exists in the same scope.  
+// Also, `console.log(decimalNumber)` is outside the function and `decimalNumber` is not 
+// defined in the global scope, so that will cause a `ReferenceError`.
+
 
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+
+function convertToPercentage(decimalNumber) {
+  const percentage = `${decimalNumber * 100}%`;
+  return percentage;
+}
+
+console.log(convertToPercentage(0.5)); 

Sprint-2/1-key-errors/2.js

@@ -2,19 +2,32 @@
 // Predict and explain first BEFORE you run any code...
 
 // this function should square any number but instead we're going to get an error
+// The code will throw a **SyntaxError** because you cannot 
+// use a number (`3`) as a function parameter name.
 
 // =============> write your prediction of the error here
+// SyntaxError: Unexpected number
 
 function square(3) {
     return num * num;
 }
 
 // =============> write the error message here
+// SyntaxError: Unexpected number
 
 // =============> explain this error message here
+// In JavaScript, function parameters must be valid variable names (identifiers).  
+// Using a number like `3` directly as a parameter name is invalid syntax, 
+// so JavaScript throws a `SyntaxError: Unexpected number`.
 
 // Finally, correct the code to fix the problem
 
 // =============> write your new code here
 
+function square(num) {
+  return num * num;
+}
+
+console.log(square(3)); 
+
 

Sprint-2/2-mandatory-debug/0.js

@@ -1,6 +1,10 @@
 // Predict and explain first...
 
 // =============> write your prediction here
+// I predict that the console will log `320` first (from inside the function), 
+// but then the message will say: "The result of multiplying 10 and 32 is undefined".
+
+// Explanation:
 
 function multiply(a, b) {
   console.log(a * b);
@@ -9,6 +13,16 @@ function multiply(a, b) {
 console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
 
 // =============> write your explanation here
+// The function `multiply` logs the result of `a * b`, but does not return it. 
+// When it's used inside a template literal, JavaScript evaluates `multiply(10, 32)` as `undefined`, 
+// because the function has no return value. That's why we get:  
+// `The result of multiplying 10 and 32 is undefined` — even though `320` is logged separately.
 
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+
+function multiply(a, b) {
+  return a * b;
+}
+
+console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);

Sprint-2/2-mandatory-debug/1.js

@@ -1,13 +1,27 @@
 // Predict and explain first...
-//  =============> write your prediction here
 
+// =============> write your prediction here
+// I predict that this will print: "The sum of 10 and 32 is undefined"
+// because the function has a return statement with no value.
+
+// Explanation:
 function sum(a, b) {
   return;
   a + b;
+  // =============> write your explanation here
+  // The `return;` statement ends the function early, so `a + b` is never reached.
+  // In JavaScript, any code after a bare `return;` is ignored (unreachable code).
+  // That's why the function returns `undefined`, not the actual sum.
 }
 
 console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
 
-// =============> write your explanation here
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function sum(a, b) {
+  return a + b;
+}
+
+console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
+// Now the function returns the correct result: 42
+

Sprint-2/2-mandatory-debug/2.js

@@ -2,7 +2,11 @@
 
 // Predict the output of the following code:
 // =============> Write your prediction here
+// I predict that all three log statements will output: "The last digit of 42 is 3", "105 is 3", "806 is 3"
+// Because the getLastDigit function doesn’t use the input — it always returns the last digit of the constant 
+// `num = 103`.
 
+// Original Code
 const num = 103;
 
 function getLastDigit() {
@@ -15,10 +19,25 @@ console.log(`The last digit of 806 is ${getLastDigit(806)}`);
 
 // Now run the code and compare the output to your prediction
 // =============> write the output here
+// The actual output is:
+// The last digit of 42 is 3
+// The last digit of 105 is 3
+// The last digit of 806 is 3
+
 // Explain why the output is the way it is
 // =============> write your explanation here
+// The function `getLastDigit` doesn't take any parameter, and it always uses the fixed variable `num = 103`.
+// So regardless of the input in the log statements, the function always returns the last digit of 103, which is "3".
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+function getLastDigit(number) {
+  return number.toString().slice(-1);
+}
+
+console.log(`The last digit of 42 is ${getLastDigit(42)}`);    // 2
+console.log(`The last digit of 105 is ${getLastDigit(105)}`);  // 5
+console.log(`The last digit of 806 is ${getLastDigit(806)}`);  // 6
+
+// Now the function works correctly by taking a number as input and returning its last digit.
 
-// This program should tell the user the last digit of each number.
-// Explain why getLastDigit is not working properly - correct the problem

Sprint-2/3-mandatory-implement/1-bmi.js

@@ -1,19 +1,13 @@
-// Below are the steps for how BMI is calculated
-
-// The BMI calculation divides an adult's weight in kilograms (kg) by their height in metres (m) squared.
-
-// For example, if you weigh 70kg (around 11 stone) and are 1.73m (around 5 feet 8 inches) tall, you work out your BMI by:
-
-// squaring your height: 1.73 x 1.73 = 2.99
-// dividing 70 by 2.99 = 23.41
-// Your result will be displayed to 1 decimal place, for example 23.4.
+function calculateBMI(weight, height) {
+  // Square the height (height in meters)
+  const heightSquared = height * height;
 
-// You will need to implement a function that calculates the BMI of someone based off their weight and height
+  // Divide weight by height squared to get BMI
+  const bmi = weight / heightSquared;
 
-// Given someone's weight in kg and height in metres
-// Then when we call this function with the weight and height
-// It should return their Body Mass Index to 1 decimal place
+  // Return the BMI rounded to 1 decimal place
+  return bmi.toFixed(1); // toFixed returns a string, which is fine unless you need it as a number
+}
 
-function calculateBMI(weight, height) {
-    // return the BMI of someone based off their weight and height
-}
+// Example usage:
+console.log(calculateBMI(70, 1.73)); // Output: "23.4"

Sprint-2/3-mandatory-implement/2-cases.js

@@ -1,16 +1,15 @@
-// A set of words can be grouped together in different cases.
+// This function converts any sentence into UPPER_SNAKE_CASE
+function toUpperSnakeCase(input) {
+  // Step 1: Convert the string to uppercase
+  const upperCase = input.toUpperCase();
 
-// For example, "hello there" in snake case would be written "hello_there"
-// UPPER_SNAKE_CASE means taking a string and writing it in all caps with underscores instead of spaces.
+  // Step 2: Replace all spaces with underscores
+  const snakeCase = upperCase.replace(/ /g, "_");
 
-// Implement a function that:
+  // Step 3: Return the result
+  return snakeCase;
+}
 
-// Given a string input like "hello there"
-// When we call this function with the input string
-// it returns the string in UPPER_SNAKE_CASE, so "HELLO_THERE"
-
-// Another example: "lord of the rings" should be "LORD_OF_THE_RINGS"
-
-// You will need to come up with an appropriate name for the function
-// Use the MDN string documentation to help you find a solution
-// This might help https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toUpperCase
+// Example usage:
+console.log(toUpperSnakeCase("hello there"));          // Output: "HELLO_THERE"
+console.log(toUpperSnakeCase("lord of the rings"));    // Output: "LORD_OF_THE_RINGS"

Sprint-2/3-mandatory-implement/3-to-pounds.js

@@ -1,6 +1,22 @@
-// In Sprint-1, there is a program written in interpret/to-pounds.js
+function toPounds(penceString) {
+  const penceStringWithoutTrailingP = penceString.substring(0, penceString.length - 1);
+  const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
 
-// You will need to take this code and turn it into a reusable block of code.
-// You will need to declare a function called toPounds with an appropriately named parameter.
+  const pounds = paddedPenceNumberString.substring(
+    0,
+    paddedPenceNumberString.length - 2
+  );
 
-// You should call this function a number of times to check it works for different inputs
+  const pence = paddedPenceNumberString
+    .substring(paddedPenceNumberString.length - 2)
+    .padEnd(2, "0");
+
+  return `£${pounds}.${pence}`;
+}
+
+// Test calls
+console.log(toPounds("399p"));   // Output: £3.99
+console.log(toPounds("5p"));     // Output: £0.05
+console.log(toPounds("45p"));    // Output: £0.45
+console.log(toPounds("999p"));   // Output: £9.99
+console.log(toPounds("2p"));     // Output: £0.02

Sprint-2/4-mandatory-interpret/time-format.js

@@ -17,18 +17,22 @@ function formatTimeDisplay(seconds) {
 // Questions
 
 // a) When formatTimeDisplay is called how many times will pad be called?
-// =============> write your answer here
+// ===> 3 times — once for hours, once for minutes, and once for seconds.
 
 // Call formatTimeDisplay with an input of 61, now answer the following:
 
 // b) What is the value assigned to num when pad is called for the first time?
-// =============> write your answer here
+// ===> 0 — the first pad call is for totalHours, which is 0 when input is 61
 
-// c) What is the return value of pad is called for the first time?
-// =============> write your answer here
+// c) What is the return value of pad when called for the first time?
+// ===> "00" — because pad(0) returns the string "00"
 
 // d) What is the value assigned to num when pad is called for the last time in this program?  Explain your answer
-// =============> write your answer here
+// ===> 1 — the last pad call is for remainingSeconds, which is 61 % 60 = 1
 
 // e) What is the return value assigned to num when pad is called for the last time in this program?  Explain your answer
-// =============> write your answer here
+// ===> "01" — because pad(1) turns 1 into "01" using padStart(2, "0")
+
+// Example run:
+console.log(formatTimeDisplay(61)); // Output: "00:01:01"
+

Sprint-2/5-stretch-extend/format-time.js

@@ -1,25 +1,46 @@
-// This is the latest solution to the problem from the prep.
-// Make sure to do the prep before you do the coursework
-// Your task is to write tests for as many different groups of input data or edge cases as you can, and fix any bugs you find.
-
 function formatAs12HourClock(time) {
   const hours = Number(time.slice(0, 2));
-  if (hours > 12) {
-    return `${hours - 12}:00 pm`;
+  const minutes = time.slice(3, 5);
+
+  let rawHour;
+  let period;
+
+  if (hours === 0) {
+    rawHour = 12;
+    period = "am";
+  } else if (hours === 12) {
+    rawHour = 12;
+    period = "pm";
+  } else if (hours > 12) {
+    rawHour = hours - 12;
+    period = "pm";
+  } else {
+    rawHour = hours;
+    period = "am";
   }
-  return `${time} am`;
+
+  const formattedHour = String(rawHour).padStart(2, "0");
+
+  return `${formattedHour}:${minutes} ${period}`;
 }
 
-const currentOutput = formatAs12HourClock("08:00");
-const targetOutput = "08:00 am";
-console.assert(
-  currentOutput === targetOutput,
-  `current output: ${currentOutput}, target output: ${targetOutput}`
-);
-
-const currentOutput2 = formatAs12HourClock("23:00");
-const targetOutput2 = "11:00 pm";
-console.assert(
-  currentOutput2 === targetOutput2,
-  `current output: ${currentOutput2}, target output: ${targetOutput2}`
-);
+
+// Tests:
+const tests = [
+  { input: "00:00", expected: "12:00 am" },
+  { input: "08:00", expected: "08:00 am" },
+  { input: "12:00", expected: "12:00 pm" },
+  { input: "15:30", expected: "03:30 pm" },
+  { input: "23:59", expected: "11:59 pm" },
+  { input: "11:15", expected: "11:15 am" },
+];
+
+tests.forEach(({ input, expected }) => {
+  const output = formatAs12HourClock(input);
+  console.assert(
+    output === expected,
+    `FAIL: input=${input}, output=${output}, expected=${expected}`
+  );
+});
+
+