London | 26-ITP-January | Eugenie Ahangama | Sprint 2 | coursework/sprint 2

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

@@ -1,13 +1,29 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// Prediction: The code will throw a SyntaxError because the variable 'str' has already been declared as a parameter of the function.
 
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
 
+// Original code with error:
+
+/*
 function capitalise(str) {
   let str = `${str[0].toUpperCase()}${str.slice(1)}`;
   return str;
 }
+  */
 
 // =============> write your explanation here
+// Explanation: The error occurs because the variable 'str' is being redeclared within the function using 'let', 
+// which is not allowed since 'str' is already declared as a parameter of the function. 
+// To fix this, we can either rename the inner variable or simply assign the new value to the existing parameter without redeclaring it.
+
 // =============> write your new code here
+// Fixed code:
+function capitalise(str) {
+  str = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return str;
+}
+
+console.log(capitalise("hello")); // Output: "Hello"

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

@@ -2,9 +2,14 @@
 
 // Why will an error occur when this program runs?
 // =============> write your prediction here
+// Prediction: The error will occur because the variable 'decimalNumber' is being redeclared 
+// inside the function using 'const', which is an illegal operation. 
+// Variables declared with 'const' cannot be redeclared in the same scope.
 
 // Try playing computer with the example to work out what is going on
 
+/*
+Original code:
 function convertToPercentage(decimalNumber) {
   const decimalNumber = 0.5;
   const percentage = `${decimalNumber * 100}%`;
@@ -13,8 +18,18 @@ function convertToPercentage(decimalNumber) {
 }
 
 console.log(decimalNumber);
+*/
 
 // =============> write your explanation here
+// Explanation: The error occurs because 'decimalNumber' is declared as a parameter of the function. 
+// When we try to declare it again inside the function with 'const', it causes a syntax error.
+// To fix this, we should either use the parameter directly or rename the inner variable.
 
 // 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)); // Output: 50%

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

@@ -4,17 +4,34 @@
 // this function should square any number but instead we're going to get an error
 
 // =============> write your prediction of the error here
+// Prediction: It will throw a syntax error because 3 is not a valid parameter name.
 
+/* Original Code:
 function square(3) {
     return num * num;
 }
+*/
 
 // =============> write the error message here
+// SyntaxError: Unexpected number
 
 // =============> explain this error message here
+// MDN Reference: https://developer.mozilla.org/en-US/docs/Glossary/Identifier
+
+// JavaScript does not allow numbers to be used as variable names or parameter names.
+// Function parameters must follow the rules for valid identifiers.
+// According to MDN, an identifier may not start with a digit and must follow JavaScript's naming rules.
 
 // Finally, correct the code to fix the problem
 
 // =============> write your new code here
+function square(num) {
+    return num * num;
+}
+
+console.log(square(3)); // 9
 
+// Test cases:
 
+// console.log(square(10)); // 100
+// console.log(square(5)); // 25

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

@@ -1,14 +1,35 @@
 // Predict and explain first...
 
 // =============> write your prediction here
+// Prediction: The function will not multiply the numbers.
+// Instead, it will print the sum of a and b (42) and the final console.log will ouput:
+// The result of multiplying 10 and 32 is undefined
 
+/* Original code
 function multiply(a, b) {
   console.log(a * b);
 }
 
 console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
+*/
+
+// =============> Error message
+// 320
+// The result of multiplying 10 and 32 is undefined
 
 // =============> write your explanation here
+// MDN Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/return
+
+// The function multiply() uses console.log() to print the result but it does not return anything.
+// In JavaScript, if a function does not explicitly return a value, it returns undefined.
+// When we try to use multiplay(10, 32) inside a console.log, it returns undefined.
+// To fix this, we must use the return statement so the function gives back a value that can be used.
 
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function multiply(a, b) {
+  return a * b;
+}
+
+// The result of multiplying 10 and 32 is 320
+console.log(`The result of multiplying 10 and 32 is ` + multiply(10, 32)); 

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

@@ -1,13 +1,32 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// Prediction: The code should output - "The sum of 10 and 32 is 42"
+// But the code will return undefined instead of 42.
 
+/* Original code
 function sum(a, b) {
   return;
   a + b;
 }
 
 console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
+*/
+
+// =============> Error message
+// The sum of 10 and 32 is undefined
 
 // =============> write your explanation here
+// MDN Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/return
+
+// The function uses `return;` without an expression.
+// According to MDN, if a return statement has no value, the function returns undefined.
+// So when `sum(10, 32)` is called, it returns undefined.
+// To fix this, the return statement must include the expression `a + b`.
+
 // 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)}`);

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

@@ -2,7 +2,9 @@
 
 // Predict the output of the following code:
 // =============> Write your prediction here
+// Prediction: The function will always return "3" because it uses the hardcoded value 103.
 
+/* Original code:
 const num = 103;
 
 function getLastDigit() {
@@ -12,13 +14,35 @@ function getLastDigit() {
 console.log(`The last digit of 42 is ${getLastDigit(42)}`);
 console.log(`The last digit of 105 is ${getLastDigit(105)}`);
 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
+// MDN Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions#function_parameters
+
+// The function does not use the input number passed in.
+// It always returns the last digit of the variable `num`, which is 103.
+// To fix this, the function should accept a parameter and use that instead of the hardcoded value.
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+function getLastDigit(num) {
+  return num.toString().slice(-1);
+}
+
+console.log(`The last digit of 42 is ${getLastDigit(42)}`);
+console.log(`The last digit of 105 is ${getLastDigit(105)}`);
+console.log(`The last digit of 806 is ${getLastDigit(806)}`);
 
 // This program should tell the user the last digit of each number.
 // Explain why getLastDigit is not working properly - correct the problem
+
+// The original function was not working as it wasn't taking any parameters and always used the variable `num = 103`.
+// So no matter what number you passed in, the function would ignore it and always returned the hardcoded value, "103" 
+// instead, which was "3", in this case.

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

@@ -16,4 +16,8 @@
 
 function calculateBMI(weight, height) {
     // return the BMI of someone based off their weight and height
-}
+    return (weight / (height * height)).toFixed(1);  // toFixed(1) rounds to 1 decimal place.
+}
+
+// Test case
+console.log(calculateBMI(70, 1.73)) // Output: 23.4

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

@@ -14,3 +14,22 @@
 // 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
+
+// MDN References I used: 
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/trim
+
+function toUpperSnakeCase(input) {
+  return input
+  // Removes extra spaces
+  .trim() 
+  // Converts everything to caps
+  .toUpperCase() 
+  // Replaces all spaces with underscores 
+  // g means global, so it applies to the whole string
+  // / / is a regular expression matching a space
+  .replace(/ /g, "_");
+}
+
+console.log(toUpperSnakeCase("hello there")); // HELLO_THERE

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

@@ -4,3 +4,26 @@
 // 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
+
+// Converts a string representing pence (e.g. "399") 
+// into pounds.pence format (e.g. "3.99")
+// MDN References used:
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substring
+
+// Converts a pence string (e.g. "399")
+function toPounds(penceString) {
+  // Ensure the string is atleast 3 characters long by padding with leading zeros if needed
+  // e.g. "5" → "005", "99" → "099", "399" stays "399"
+  const padded = penceString.padStart(3, "0");
+  // Extract everything except the last two digits → this becomes the pounds
+  // e.g. "399" → "3"
+  const pounds = padded.substring(0, padded.length - 2);
+  // Extract the last two digits → this becomes the pence 
+  // e.g. "399" → "99"
+  const pence = padded.substring(padded.length - 2);
+  // Combines pounds and pence into the final money format
+  return `${pounds}.${pence}`;
+}
+
+console.log(toPounds("399")); // 3.99

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

@@ -18,17 +18,42 @@ function formatTimeDisplay(seconds) {
 
 // a) When formatTimeDisplay is called how many times will pad be called?
 // =============> write your answer here
+// pad(totalHours)
+// pad(remainingMinutes)
+// pad(remainingSeconds)
+// Answer: 3
 
 // 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
+// formatTimeDisplay:
+// seconds = 61
+// remainingSeconds = 61 % 60 = 1
+// totalMinutes = (61 - 1) / 60 = 1
+// remainingMinutes = 1 % 60 = 1
+// totalHours = (1 - 1) / 60 = 0
+// Answer: pad(num) = pad(0) = 0
 
 // c) What is the return value of pad is called for the first time?
 // =============> write your answer here
+// First call: pad(totalHours)
+// totalHours = 0
+// pad(0) → "00"
+// Answer: "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
+// Last call: pad(remainingSeconds)
+// remainingSeconds = 1
+// pad(1) → num = 1
+// Answer: num = 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
+// Last call: pad(remainingSeconds)
+// remainingSeconds = 1
+// toString() → "1"
+// "1".padStart(2, "0") → "01"
+// pad(1) → "01"
+// Answer = "01"