West-Midlands | 26-ITP-May | Maryam Janjua | Sprint 2 | Complete Sprint 2 Exercises

Sprint-2/1-key-exercises/1-count.js

@@ -4,3 +4,5 @@ count = count + 1;
 
 // Line 1 is a variable declaration, creating the count variable with an initial value of 0
 // Describe what line 3 is doing, in particular focus on what = is doing
+// Line 3 is evaluated from the right side. It adds 1 to the current value of count,
+// then assigns the new value back to the count variable.

Sprint-2/1-key-exercises/2-initials.js

@@ -5,6 +5,6 @@ const lastName = "Johnson";
 // Declare a variable called initials that stores the first character of each string.
 // This should produce the string "CKJ", but you must not write the characters C, K, or J in the code of your solution.
 
-const initials = ``;
+const initials = firstName[0] + middleName[0] + lastName[0];
+console.log(initials);
 
-// https://www.google.com/search?q=get+first+character+of+string+mdn

Sprint-2/1-key-exercises/3-paths.js

@@ -17,7 +17,7 @@ console.log(`The base part of ${filePath} is ${base}`);
 // Create a variable to store the dir part of the filePath variable
 // Create a variable to store the ext part of the variable
 
-const dir = ;
-const ext = ;
+const dir = filePath.slice(0, lastSlashIndex);
+const ext = filePath.slice(filePath.lastIndexOf("."));
 
 // https://www.google.com/search?q=slice+mdn

Sprint-2/1-key-exercises/4-random.js

@@ -2,8 +2,14 @@ const minimum = 1;
 const maximum = 100;
 
 const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
-
+console.log(num);
 // In this exercise, you will need to work out what num represents?
 // Try breaking down the expression and using documentation to explain what it means
 // It will help to think about the order in which expressions are evaluated
 // Try logging the value of num and running the program several times to build an idea of what the program is doing
+
+// num represents a random whole number between 1 and 100, including both 1 and 100.
+// Math.random() generates a random number from 0 up to, but not including, 1.
+// Multiplying by (maximum - minimum + 1) creates the required range.
+// Math.floor() rounds the result down to a whole number.
+// Adding minimum makes the final range start at 1.

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

@@ -1,4 +1,7 @@
-// trying to create an age variable and then reassign the value by 1
+// The error occurs because age is declared with const, so its value cannot be reassigned.
+// The next line tries to assign a new value to age, which causes a TypeError.
+// Using let fixes the error because let allows the variable to be reassigned.
 
-const age = 33;
+let age = 33;
 age = age + 1;
+console.log(age);

Sprint-2/2-mandatory-errors/2.js

@@ -1,5 +1,10 @@
 // Currently trying to print the string "I was born in Bolton" but it isn't working...
 // what's the error ?
 
-console.log(`I was born in ${cityOfBirth}`);
 const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);
+
+// The error occurs because cityOfBirth is accessed before it has been initialized.
+// Variables declared with const cannot be accessed before their declaration is executed.
+// This causes a ReferenceError because the variable is in the Temporal Dead Zone (TDZ).
+// Moving the declaration before console.log fixes the error because cityOfBirth has a value before it is used.

Sprint-2/2-mandatory-errors/3.js

@@ -1,9 +1,13 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
-
-// The last4Digits variable should store the last 4 digits of cardNumber
-// However, the code isn't working
-// Before running the code, make and explain a prediction about why the code won't work
-// Then run the code and see what error it gives.
-// Consider: Why does it give this error? Is this what I predicted? If not, what's different?
-// Then try updating the expression last4Digits is assigned to, in order to get the correct value
+const last4Digits = cardNumber.toString().slice(-4);
+
+console.log(last4Digits);
+
+// Prediction: the code will not work because cardNumber is a number,
+// and the slice() method cannot be used directly on numbers.
+
+// Running the original code gives a TypeError because cardNumber.slice is not a function.
+// This happens because slice() is available for strings and arrays, but not for numbers.
+
+// Converting cardNumber to a string first allows slice(-4) to return the last four characters.
+// Therefore, last4Digits stores "4213".

Sprint-2/2-mandatory-errors/4.js

@@ -1,2 +1,7 @@
-const 12HourClockTime = "8:53pm";
-const 24hourClockTime = "20:53";
+const twelveHourClockTime = "8:53pm";
+const twentyFourHourClockTime = "20:53";
+
+// The error occurs because JavaScript variable names cannot start with a number.
+// Both variable names begin with digits, so JavaScript cannot parse them as valid identifiers
+// and throws a SyntaxError.
+// Renaming the variables so they start with letters fixes the error.

Sprint-2/3-mandatory-interpret/1-percentage-change.js

@@ -2,7 +2,7 @@ let carPrice = "10,000";
 let priceAfterOneYear = "8,543";
 
 carPrice = Number(carPrice.replaceAll(",", ""));
-priceAfterOneYear = Number(priceAfterOneYear.replaceAll("," ""));
+priceAfterOneYear = Number(priceAfterOneYear.replaceAll(",", ""));
 
 const priceDifference = carPrice - priceAfterOneYear;
 const percentageChange = (priceDifference / carPrice) * 100;
@@ -12,11 +12,31 @@ console.log(`The percentage change is ${percentageChange}`);
 // Read the code and then answer the questions below
 
 // a) How many function calls are there in this file? Write down all the lines where a function call is made
+// There are 5 function/method calls:
+// Line 4: carPrice.replaceAll(",", "")
+// Line 4: Number(...)
+// Line 5: priceAfterOneYear.replaceAll(",", "")
+// Line 5: Number(...)
+// Line 10: console.log(...)
 
 // b) Run the code and identify the line where the error is coming from - why is this error occurring? How can you fix this problem?
+// The error originally comes from line 5.
+// priceAfterOneYear was declared with const, but line 5 tries to assign a new value to it.
+// A variable declared with const cannot be reassigned, so JavaScript throws a TypeError.
+// To fix the error, change const to let because priceAfterOneYear needs to be reassigned.
 
 // c) Identify all the lines that are variable reassignment statements
+// Line 4: carPrice = Number(carPrice.replaceAll(",", ""));
+// Line 5: priceAfterOneYear = Number(priceAfterOneYear.replaceAll(",", ""));
 
 // d) Identify all the lines that are variable declarations
+// Line 1: let carPrice = "10,000";
+// Line 2: let priceAfterOneYear = "8,543";
+// Line 7: const priceDifference = carPrice - priceAfterOneYear;
+// Line 8: const percentageChange = (priceDifference / carPrice) * 100;
 
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+// carPrice.replaceAll(",", "") removes all commas from the string,
+// changing "10,000" to "10000".
+// Number(...) then converts the string "10000" into the number 10000.
+// This allows carPrice to be used correctly in mathematical calculations.

Sprint-2/3-mandatory-interpret/2-time-format.js

@@ -1,25 +1,71 @@
 const movieLength = 8784; // length of movie in seconds
 
+// Test values tried:
+// const movieLength = 9893;
+// const movieLength = 223;
+// const movieLength = 50;
+// const movieLength = 345;
+// const movieLength = 600;
+// const movieLength = 400;
+// const movieLength = 90;
+// const movieLength = 189;
+
+function movieFormatting(num) {
+    if (num < 10) {
+        return "0" + num.toString();
+    } else {
+        return num.toString();
+    }
+}
+
 const remainingSeconds = movieLength % 60;
 const totalMinutes = (movieLength - remainingSeconds) / 60;
 
 const remainingMinutes = totalMinutes % 60;
 const totalHours = (totalMinutes - remainingMinutes) / 60;
 
-const result = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
+const result = `${movieFormatting(totalHours)}:${movieFormatting(remainingMinutes)}:${movieFormatting(remainingSeconds)}`;
 console.log(result);
 
 // For the piece of code above, read the code and then answer the following questions
 
 // a) How many variable declarations are there in this program?
+// There are 6 variable declarations in the original program:
+// movieLength, remainingSeconds, totalMinutes, remainingMinutes, totalHours, and result.
 
 // b) How many function calls are there?
+// There is 1 function call in the original program:
+// console.log(result).
 
 // c) Using documentation, explain what the expression movieLength % 60 represents
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
+// The % operator is the remainder operator. It returns the remainder after division.
+// Here, movieLength % 60 gives the number of seconds left over after dividing
+// the total movie length in seconds by 60.
+// For example, with movieLength = 8784, the remainder is 24,
+// so remainingSeconds is 24.
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// First, remainingSeconds is subtracted from movieLength.
+// This removes the leftover seconds and leaves a value that can be divided
+// evenly by 60. The result is then divided by 60 to convert the seconds
+// into the total number of whole minutes.
+// For movieLength = 8784, totalMinutes is 146.
 
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
+// result represents the movie duration in hours, minutes and seconds.
+// A more descriptive variable name could be movieDurationHHMMSS.
+// For movieLength = 8784, the formatted result is "02:26:24".
 
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+// I tested the code with multiple values of movieLength, including:
+// 9893, 223, 50, 345, 600, 400, 90 and 189.
+
+// The original code works for the positive whole-number values I tested,
+// but it does not always format the output in HH:MM:SS format.
+// If the hours, minutes, or seconds are less than 10, for example 5 or 7,
+// they are displayed as a single digit instead of two digits.
+
+// I created the movieFormatting() function to add a leading 0 when a value
+// is less than 10. Otherwise, the function returns the value as a string.
+// I then tested the updated code with multiple movieLength values and
+// the tested values produced the expected HH:MM:SS formatted output.

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

@@ -1,27 +1,74 @@
 const penceString = "399p";
-
 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");
-
 console.log(`£${pounds}.${pence}`);
+// This program takes a string representing a price in pence.
+// The program then builds up a string representing the price in pounds.
+
+// Step-by-step breakdown:
+
+// 1. const penceString = "399p";
+// Initialises the penceString variable with the string "399p".
+// This represents a price of 399 pence.
+
+// 2. penceString.length - 1
+// penceString has a length of 4. Subtracting 1 gives 3.
+// This is used to identify the position before the final "p".
+
+// 3. penceString.substring(0, penceString.length - 1)
+// substring() extracts the characters from index 0 up to, but not including,
+// index 3. This removes the trailing "p" and produces the string "399".
+
+// 4. const penceStringWithoutTrailingP = ...
+// Stores the result "399", so the price now contains only the numeric characters.
+
+// 5. penceStringWithoutTrailingP.padStart(3, "0")
+// padStart() makes sure the string contains at least 3 characters.
+// If it has fewer than 3 characters, "0" is added to the beginning.
+// For "399", no padding is needed, so the value remains "399".
+// This is useful for smaller values such as "99", which would become "099".
+
+// 6. const paddedPenceNumberString = ...
+// Stores the padded string. For the current input, its value is "399".
+
+// 7. paddedPenceNumberString.length - 2
+// This calculates the position that separates the pounds from the final
+// two digits representing pence. For "399", the length is 3, so 3 - 2 = 1.
+
+// 8. paddedPenceNumberString.substring(
+//      0,
+//      paddedPenceNumberString.length - 2
+//    )
+// Extracts the characters before the final two digits.
+// For "399", this extracts "3", which represents the pounds.
+
+// 9. const pounds = ...
+// Stores the pounds part of the price. In this example, pounds is "3".
+
+// 10. paddedPenceNumberString
+//       .substring(paddedPenceNumberString.length - 2)
+// substring() starts two characters from the end of the string.
+// For "399", it extracts "99", which represents the pence part.
 
-// This program takes a string representing a price in pence
-// The program then builds up a string representing the price in pounds
+// 11. .padEnd(2, "0")
+// Makes sure the pence part contains at least two characters.
+// If necessary, "0" is added to the end until the string has a length of 2.
+// In this example, "99" already has two characters, so it remains "99".
 
-// You need to do a step-by-step breakdown of each line in this program
-// Try and describe the purpose / rationale behind each step
+// 12. const pence = ...
+// Stores the final pence part. In this example, pence is "99".
 
-// To begin, we can start with
-// 1. const penceString = "399p": initialises a string variable with the value "399p"
+// 13. console.log(`£${pounds}.${pence}`);
+// Uses a template literal to combine the pound sign, pounds value,
+// decimal point and pence value.
+// With the input "399p", the final output is "£3.99".