London | May 2025 | Samuel Tarawally | Sprint 2 | Coursework

.gitignore

@@ -1,4 +1,6 @@
 node_modules
 .DS_Store
 .vscode
-**/.DS_Store
+**/.DS_Store
+**/runme.md
+.devcontainer/

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

@@ -1,5 +1,6 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// A syntax error should occur because the function parameter is named `str`, but it is also being redeclared inside the function.
 
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
@@ -10,4 +11,11 @@ function capitalise(str) {
 }
 
 // =============> write your explanation here
+// The code outputs the error `SyntaxError: Identifier 'str' has already been declared`.
+// JavaScript does not allow you to redeclare a variable or parameter with the same name in the same scope.
+// In this case, the parameter `str` is being redeclared as a `let` variable inside the function, which is not allowed.
 // =============> write your new code here
+function capitalise(str) {
+  const capitalisedString = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return capitalisedString;
+}

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

@@ -2,6 +2,7 @@
 
 // Why will an error occur when this program runs?
 // =============> write your prediction here
+// An error such as `decimalNumber is not defined` will occur because `decimalNumber` is not defined in the global scope.
 
 // Try playing computer with the example to work out what is going on
 
@@ -15,6 +16,17 @@ function convertToPercentage(decimalNumber) {
 console.log(decimalNumber);
 
 // =============> write your explanation here
+// The first error occurs when attempting to run `console.log(decimalNumber)`, resulting in a `SyntaxError: Identifier 'decimalNumber' has already been declared`.
+// This happens because `decimalNumber` is declared twice within the same scope: once as a parameter of the function and again as a constant inside the function.
+// The second error is that `decimalNumber` is not defined in the global scope.
+// Therefore, trying to log it outside the function will result in a `ReferenceError: decimalNumber is not defined`.
+// Instead, the function should use the parameter `decimalNumber` directly without redeclaring it.
 
 // 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

@@ -1,20 +1,26 @@
-
 // Predict and explain first BEFORE you run any code...
 
 // this function should square any number but instead we're going to get an error
 
 // =============> write your prediction of the error here
+// A SyntaxError will occur because you cannot use a number such as `3` as a function parameter name.
+// Names for parameters must be valid identifiers, for example, starting with a letter or underscore.
 
 function square(3) {
     return num * num;
 }
 
 // =============> write the error message here
+// `SyntaxError: Unexpected number`
 
 // =============> explain this error message here
+// Function parameters are placeholders for the values that will be passed into the function.
+// These placeholders must follow the same naming rules as variables, and a variable name cannot be a number.
+// In this instance, the code `function square(3)` is attempting to declare a parameter with the name `3`, which is not a valid identifier, hence the `SyntaxError`.
 
 // Finally, correct the code to fix the problem
 
 // =============> write your new code here
-
-
+function squareFixed(num) {
+  return num * num;
+}

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

@@ -1,6 +1,10 @@
 // Predict and explain first...
 
 // =============> write your prediction here
+// The console will output two lines.
+//    1. `320` (from inside the multiply function)
+//    2. `The result of multiplying 10 and 32 is undefined`
+// This is because the `multiply` function logs the result but does not return it, as functions that do not explicitly return a value return `undefined` by default.
 
 function multiply(a, b) {
   console.log(a * b);
@@ -9,6 +13,13 @@ function multiply(a, b) {
 console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
 
 // =============> write your explanation here
+// The bug occurs because the `multiply` function uses `console.log()` to display the result instead of using the `return` keyword.
+// When the function call is placed inside the template literal, it resolves to its return value, which is `undefined`.
 
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function multiplyFixed(a, b) {
+  return a * b;
+}
+
+console.log(`The result of multiplying 10 and 32 is ${multiplyFixed(10, 32)}`);

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

@@ -1,5 +1,7 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// The output should be `The sum of 10 and 32 is undefined` given that the `return;` statement is on a line by itself before the actual calculation.
+// This should cause the function to exit and return `undefined`.
 
 function sum(a, b) {
   return;
@@ -9,5 +11,14 @@ function sum(a, b) {
 console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
 
 // =============> write your explanation here
+// The `return` keyword immediately stops the execution of a function and returns a value.
+// Here, `return;` is called without a value, so the function exits and returns `undefined`.
+// As a result, the line `a + b;` is never executed.
+
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function sumFixed(a, b) {
+  return a + b;
+}
+
+console.log(`The sum of 10 and 32 is ${sumFixed(10, 32)}`);

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

@@ -2,6 +2,8 @@
 
 // Predict the output of the following code:
 // =============> Write your prediction here
+// The output will be the same, `3`, for all three calls.
+// This is because the function ignores its input parameter and always operates on the global constant `num`.
 
 const num = 103;
 
@@ -15,10 +17,22 @@ 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 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` is defined without any parameters, so it cannot use the numbers (42, 105, 806) being passed to it.
+// Instead the function accesses the global constant `num` (which is 103) every time it is called.
+// Therefore, it always resolves the last digit of 103, which is '3'.
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+function getLastDigitFixed(inputNumber) {
+  return inputNumber.toString().slice(-1);
+}
 
-// This program should tell the user the last digit of each number.
-// Explain why getLastDigit is not working properly - correct the problem
+console.log(`The last digit of 42 is ${getLastDigitFixed(42)}`);
+console.log(`The last digit of 105 is ${getLastDigitFixed(105)}`);
+console.log(`The last digit of 806 is ${getLastDigitFixed(806)}`);

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

@@ -15,5 +15,8 @@
 // It should return their Body Mass Index to 1 decimal place
 
 function calculateBMI(weight, height) {
-    // return the BMI of someone based off their weight and height
-}
+  const bmi = weight / (height * height);
+  return parseFloat(bmi.toFixed(1));
+}
+
+console.log(`BMI for 82.4kg, 1.82m: ${calculateBMI(82.4, 1.82)}`);

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

@@ -14,3 +14,11 @@
 // 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
+
+function toUpperSnakeCase(inputString) {
+  return inputString.toUpperCase().replaceAll(" ", "_");
+}
+
+console.log(
+  `"a wizard of earthsea" becomes: ${toUpperSnakeCase("a wizard of earthsea")}`
+);

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

@@ -4,3 +4,24 @@
 // You will need to declare a function called toPounds with an appropriately named parameter.
 
 // You should call this function a number of times to check it works for different inputs
+
+function toPounds(penceString) {
+  const penceStringWithoutTrailingP = penceString.substring(
+    0,
+    penceString.length - 1
+  );
+
+  const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+  const pounds = paddedPenceNumberString.substring(
+    0,
+    paddedPenceNumberString.length - 2
+  );
+
+  const pence = paddedPenceNumberString
+    .substring(paddedPenceNumberString.length - 2)
+    .padEnd(2, "0");
+
+  return `£${pounds}.${pence}`;
+}
+
+console.log(`"399p" converts to: ${toPounds("399p")}`);

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

@@ -18,17 +18,25 @@ function formatTimeDisplay(seconds) {
 
 // a) When formatTimeDisplay is called how many times will pad be called?
 // =============> write your answer here
+// The `pad` function will be called 3 times. This is because the return statement in `formatTimeDisplay` calls `pad` for `totalHours`, `remainingMinutes`, and `remainingSeconds`.
 
 // 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
+// The value assigned to `num` will be `0`.
 
 // c) What is the return value of pad is called for the first time?
 // =============> write your answer here
+// The return value will be 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
+// The value assigned to `num` will be `1`.
+// With an input of 61, `remainingSeconds` is calculated as `61 % 60`, which is `1`.
+// The last call to `pad` in the `return` statement uses `remainingSeconds` as its argument.
 
 // 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
+// The return value will be the string `"01"`.
+// The `pad` function takes the number `1`, converts it to the string `"1"`, and then uses `padStart(2, "0")` to add a leading zero, resulting in `"01"`.