London | May 2025 | Houssam Lahlah | Coursework/sprint 1

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

@@ -4,3 +4,4 @@ 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 increases the value of count by 1 and saves the updated value back into count variable.

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

@@ -5,7 +5,10 @@ let 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.
 
-let initials = ``;
 
-// https://www.google.com/search?q=get+first+character+of+string+mdn
+let initials = firstName.charAt(0) + middleName.charAt(0) + lastName.charAt(0);
+
+console.log(initials);
 
+
+// https://www.google.com/search?q=get+first+character+of+string+mdn

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

@@ -17,7 +17,8 @@ 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 = base.slice(base.lastIndexOf(".") + 1);
+
 
 // https://www.google.com/search?q=slice+mdn

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

@@ -3,7 +3,74 @@ const maximum = 100;
 
 const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
 
-// 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
+// 1- In this exercise, you will need to work out what num represents?
+
+// the num gives a random whole number between 1 and 100 like 73, 12, or 100.
+
+// 2- Try breaking down the expression and using documentation to explain what it means
+/*
+
+1. Math.random()
+
+Returns a random decimal number between 0 and 1 but never gives 1.0.
+
+Example: 0.24 
+
+2. (maximum - minimum + 1)
+
+This gives number of possible values.
+
+Without the +1, we'd only get the difference, not the full count.
+
+for example:
+
+5 - 1 = 4 → but there are actually 5 numbers: 1, 2, 3, 4, 5
+
+So we add +1 to include both ends of the range.
+
+3. Math.random() * (maximum - minimum + 1)
+
+This gives a random decimal number between 0 and 100 (like 24, 65 ...)
+
+Because we want the random decimal scaled to the size of the range of possible values.
+
+For example, if we want a number between 1 and 100 (inclusive), there are 100 possible numbers (1, 2, ..., 100).
+
+Multiplying by 100 means the decimal is scaled up to cover all those possibilities before rounding.
+
+4. Math.floor(...)
+
+This rounds the decimal down to the nearest whole number.
+
+Example: Math.floor(78.43) → 78
+
+5. + minimum
+
+we add the minimum to shift the range correctly, and make sure the random number up to start from minimum.
+
+5-1- for example if we remove the + minimum 
+
+5-1-1 Math.random() 0.9999 * 99 + 1 → only goes up to 99.999... → max = 99.999... → floor = 100 (but very unlikely) 
+
+now 100 becomes very hard to reach, and in many cases, you never get it.
+
+5-1-2 Math.random() 0.00 * 99 + 1 → only goes up to 0... → max = 0... → floor = 0 (now the minimum is 0, and can appears) 
+
+conclusion : when we don’t add + minimum, there is a chance that 1 appears, but it’s not the guaranteed minimum anymore — 
+
+and the range starts at 0, not 1.
+
+5-2- when we add +minimum 
+
+now we make sure the min and max can appear in the final results and make sure the minimum is 1 not 0. 
+
+Minimum appears when random = 0
+
+Maximum appears when random is almost 1 (like 0.9999...).
+
+example : Math.random() * 99 + 1 → up to 0.99 → max = 99 → floor = 99 → +1 = 100 (so more possibilities for 100 to appears) 
+
+*/
+
+//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

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

@@ -1,2 +1,16 @@
+ // we can turn the lines into comments. we can use:
+
+// for single-line comments, or
+
+/* for multi-line comments. */
+
+/*
+
 This is just an instruction for the first activity - but it is just for human consumption
-We don't want the computer to run these 2 lines - how can we solve this problem?
+We don't want the computer to run these 2 lines - how can we solve this problem?  
+
+*/
+
+// we can use comments to make sure the computer ignores the lines, comment them out using :  
+
+// // single line  or /* multi-line */.

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

@@ -1,4 +1,5 @@
-// trying to create an age variable and then reassign the value by 1
+// Trying to create an age variable and then reassign the value by 1
 
-const age = 33;
-age = age + 1;
+let age = 33;          // Declare a variable called age and assign it the value 33
+age = age + 1;         // Reassign age to be its current value plus 1
+console.log(age);      // Output: 34

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

@@ -1,5 +1,7 @@
 // Currently trying to print the string "I was born in Bolton" but it isn't working...
-// what's the error ?
+// what's the error ?   The error here is due to using a variable before it's declared.
 
-console.log(`I was born in ${cityOfBirth}`);
+
+// Fixed: Declare the variable before using it
 const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);

Sprint-1/2-mandatory-errors/3.js

@@ -1,9 +1,22 @@
 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
+
+// We want last4Digits to store the last 4 digits of cardNumber
+
+// Prediction before running:
+// This will cause an error because cardNumber is a number,
+// and numbers don't have the slice() method. slice() works only on strings or arrays.
+
+// Running the code would give:
+// TypeError: cardNumber.slice is not a function
+
+// Why?
+// Because slice() is not defined for numbers in JavaScript.
+
+// Fix:
+// Convert cardNumber to a string first, so we can use slice() on it.
+// Then slice the last 4 characters to get the last 4 digits.
+
+const last4Digits = String(cardNumber).slice(-4);
+
+console.log(last4Digits);       // Output: 4213
+

Sprint-1/2-mandatory-errors/4.js

@@ -1,2 +1,14 @@
-const 12HourClockTime = "20:53";
-const 24hourClockTime = "08:53";
+// Original variable names are invalid because variable names cannot start with a number
+// const 12HourClockTime = "20:53"; //  This will cause a syntax error
+// const 24hourClockTime = "08:53"; //  Also invalid for the same reason
+
+// Fix:
+// Variable names must start with a letter, underscore (_), or dollar sign ($).
+// So we rename the variables to valid names below:
+
+const hour12ClockTime = "20:53";  // Valid variable name for 12-hour clock time
+const hour24ClockTime = "08:53";  // Valid variable name for 24-hour clock time
+
+// Explanation:
+// Variable names cannot begin with a number in JavaScript,
+// so prefixing them with a letter or underscore solves the problem.

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

@@ -11,12 +11,41 @@ console.log(`The percentage change is ${percentageChange}`);
 
 // Read the code and then answer the questions below
 
+// --- Answers to the questions ---
+
 // a) How many function calls are there in this file? Write down all the lines where a function call is made
 
+// Function calls:
+// - Line 4: carPrice.replaceAll(",", "")
+// - Line 4: Number(...)
+// - Line 5: priceAfterOneYear.replaceAll("," "") --> syntax error here
+// - 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?
 
+// Error at line 5: SyntaxError due to missing comma in replaceAll arguments
+// Fix: add the missing comma inside replaceAll:
+// priceAfterOneYear.replaceAll(",", "")
+
 // c) Identify all the lines that are variable reassignment statements
 
+// Reassignments:
+// - Line 4: carPrice = Number(...)
+// - Line 5: priceAfterOneYear = Number(...)
+
 // d) Identify all the lines that are variable declarations
 
+// Declarations:
+// - Line 1: let carPrice = "10,000";
+// - Line 2: let priceAfterOneYear = "8,543";
+// - Line 7: const priceDifference = ...
+// - Line 10: const percentageChange = ...
+
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+
+// Explanation:
+// - carPrice.replaceAll(",","") removes all commas from the string "10,000", turning it into "10000".
+// - Number(...) converts the resulting string "10000" into the numeric value 10000.
+// This allows mathematical operations on carPrice, which is originally a formatted string.
+

Sprint-1/3-mandatory-interpret/2-time-format.js

@@ -9,17 +9,36 @@ const totalHours = (totalMinutes - remainingMinutes) / 60;
 const result = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
 console.log(result);
 
-// For the piece of code above, read the code and then answer the following questions
+// --- Answers to the questions ---
 
 // a) How many variable declarations are there in this program?
+// There are 6 variable declarations:
+// movieLength, remainingSeconds, totalMinutes, remainingMinutes, totalHours, and result
 
 // b) How many function calls are there?
+// There is 1 function call:
+// 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 modulo operator, which returns the remainder after division.
+// So movieLength % 60 gives the remainder when movieLength is divided by 60.
+// This means it calculates the leftover seconds after counting full minutes.
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// Line 4: (movieLength - remainingSeconds) / 60
+// This subtracts the leftover seconds from the total seconds,
+// giving a multiple of 60 seconds (full minutes),
+// then divides by 60 to convert seconds to total minutes.
 
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
+// result holds the formatted string showing the movie length in "hours:minutes:seconds" format.
+// A better name might be `formattedTime` or `movieDurationFormatted`.
 
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+// For positive integers, the code works correctly.
+// For zero, it returns "0:0:0", which is fine.
+// For negative numbers, the calculation may produce unexpected negative values.
+// For very large values, it still works fine.
+// The code assumes movieLength is an integer number of seconds.
+// If movieLength is a non-integer or not a number, the code might not behave as expected.
+

Sprint-1/3-mandatory-interpret/3-to-pounds.js

@@ -1,27 +1,31 @@
 const penceString = "399p";
+// 1. Initializes a string variable with the value "399p" representing the price in pence with a trailing 'p'.
 
 const penceStringWithoutTrailingP = penceString.substring(
   0,
   penceString.length - 1
 );
+// 2. Removes the trailing 'p' by taking a substring from index 0 up to (but not including) the last character.
+//    Result: "399"
 
 const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+// 3. Ensures the string is at least 3 characters long by padding with leading zeros if needed.
+//    In this case, "399" is already 3 characters, so it remains "399".
+
 const pounds = paddedPenceNumberString.substring(
   0,
   paddedPenceNumberString.length - 2
 );
+// 4. Extracts the pounds part by taking all characters except the last two.
+//    For "399", this is "3" (the hundreds place).
 
 const pence = paddedPenceNumberString
   .substring(paddedPenceNumberString.length - 2)
   .padEnd(2, "0");
+// 5. Extracts the last two characters as the pence part.
+//    For "399", this is "99".
+//    Then pads the string on the right with zeros if it’s shorter than 2 characters (not needed here).
 
 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
-
-// You need to do a step-by-step breakdown of each line in this program
-// Try and describe the purpose / rationale behind each step
-
-// To begin, we can start with
-// 1. const penceString = "399p": initialises a string variable with the value "399p"
+// 6. Prints the formatted price string with a £ sign, pounds, and pence separated by a dot.
+//    Output: "£3.99"

Sprint-1/4-stretch-explore/chrome.md

@@ -10,9 +10,23 @@ Let's try an example.
 In the Chrome console,
 invoke the function `alert` with an input string of `"Hello world!"`;
 
-What effect does calling the `alert` function have?
+1. What effect does calling the `alert` function have? 
 
-Now try invoking the function `prompt` with a string input of `"What is your name?"` - store the return value of your call to `prompt` in an variable called `myName`.
+It opens a popup message box in the browser with the text:
+You must click "OK" to dismiss it before you can do anything else on the page.
 
-What effect does calling the `prompt` function have?
-What is the return value of `prompt`?
+2. Now try invoking the function `prompt` with a string input of `"What is your name?"` - 
+
+store the return value of your call to `prompt` in an variable called `myName`.
+
+3. What effect does calling the `prompt` function have? 
+
+It opens a popup input box asking:
+What is your name?
+and I can enter a response, then click "OK" or "Cancel".
+
+4. What is the return value of `prompt`? Return value:
+
+If I enter a name (e.g., "Sami") and press OK, it returns the string: "Sami"
+
+If I press Cancel, it returns: null