Birmingham | 26-ITP-May | Gabriel Pawuoi | Sprint 1 | Coursework

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

@@ -3,4 +3,5 @@ let count = 0;
 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 a variable reassignment. The = (assignment operator) takes the result of count + 1
+// (which evaluates to 1) and stores it back into the existing count variable, replacing the old value.

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

@@ -5,7 +5,7 @@ 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 = ``;
+let initials = `${firstName[0]}${middleName[0]}${lastName[0]}`;
 
 // https://www.google.com/search?q=get+first+character+of+string+mdn
 

Sprint-1/1-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 = base.slice(base.lastIndexOf("."));
 
 // https://www.google.com/search?q=slice+mdn

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

@@ -3,7 +3,15 @@ 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 integer between 1 and 100 (inclusive).
+//
+// Breakdown:
+// 1. Math.random() generates a random decimal in [0, 1)
+// 2. (maximum - minimum + 1) = 100, so Math.random() * 100 gives a decimal in [0, 100)
+// 3. Math.floor(...) rounds down to an integer in [0, 99]
+// 4. Adding minimum (1) shifts the range to [1, 100]
+//
+// So num is a random whole number from 1 to 100.

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

@@ -1,2 +1,3 @@
-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?
+// 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?
+// Solution: Prefix each line with // to make them comments, as done here.

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

@@ -1,4 +1,6 @@
 // trying to create an age variable and then reassign the value by 1
+// Error: Assignment to constant variable.
+// const variables cannot be reassigned. Fix: use let instead.
 
-const age = 33;
+let age = 33;
 age = age + 1;

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

@@ -1,5 +1,6 @@
 // Currently trying to print the string "I was born in Bolton" but it isn't working...
-// what's the error ?
+// Error: ReferenceError - cityOfBirth is used before it is declared.
+// const is not hoisted like var. Fix: declare the variable before using it.
 
-console.log(`I was born in ${cityOfBirth}`);
 const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);

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

@@ -1,9 +1,9 @@
+// Prediction: .slice() is a string method, not a number method, so it will throw a TypeError.
+// Error: TypeError: cardNumber.slice is not a function
+// Fix: convert the number to a string first.
+
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
+const last4Digits = cardNumber.toString().slice(-4);
 
+console.log(last4Digits);
 // 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

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

@@ -1,2 +1,7 @@
-const 12HourClockTime = "8:53pm";
-const 24hourClockTime = "20:53";
+// Error: variable names cannot start with a digit.
+// Fix: rename the variables to valid identifiers.
+const twelveHourClockTime = "8:53pm";
+const twentyFourHourClockTime = "20:53";
+
+console.log(twentyFourHourClockTime);
+console.log(twelveHourClockTime);

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

@@ -2,21 +2,25 @@ 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;
 
 console.log(`The percentage change is ${percentageChange}`);
 
-// Read the code and then answer the questions below
+// a) Function calls:
+//    Line 4: replaceAll(",", "") and Number(...)
+//    Line 5: replaceAll(",", "") and Number(...)
+//    Line 10: console.log(...)
 
-// a) How many function calls are there in this file? Write down all the lines where a function call is made
+// b) The error on line 5 is a missing comma between the two arguments to replaceAll:
+//    replaceAll("," "") should be replaceAll(",", ""). Fixed above.
 
-// 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?
+// c) Variable reassignment statements: lines 4 and 5 (carPrice = ..., priceAfterOneYear = ...)
 
-// c) Identify all the lines that are variable reassignment statements
+// d) Variable declarations: lines 1, 2 (let), lines 7, 8 (const)
 
-// d) Identify all the lines that are variable declarations
-
-// e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+// e) Number(carPrice.replaceAll(",","")) first removes all commas from the string "10,000"
+//    turning it into "10000", then converts that string into the number 10000.
+//    This is necessary because you cannot do arithmetic on strings.

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

@@ -9,17 +9,22 @@ 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
+// a) There are 6 variable declarations: movieLength, remainingSeconds, totalMinutes,
+//    remainingMinutes, totalHours, result.
 
-// a) How many variable declarations are there in this program?
+// b) There is 1 function call: console.log(result) on line 10.
 
-// b) How many function calls are there?
+// c) movieLength % 60 uses the modulo (remainder) operator.
+//    It gives the remainder after dividing movieLength by 60, i.e. the leftover seconds
+//    that don't make a full minute.
 
-// c) Using documentation, explain what the expression movieLength % 60 represents
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
+// d) totalMinutes = (movieLength - remainingSeconds) / 60
+//    First, the remaining seconds are subtracted so the value is an exact multiple of 60.
+//    Dividing by 60 then converts the total seconds into whole minutes.
 
-// d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// e) result represents the movie length formatted as HH:MM:SS (hours:minutes:seconds).
+//    A clearer name would be formattedDuration or timeDisplay.
 
-// e) What do you think the variable result represents? Can you think of a better name for this variable?
-
-// f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+// f) The code works for any non-negative integer value of movieLength.
+//    It will not work correctly for negative values (a negative duration makes no sense)
+//    but for any valid seconds value >= 0 the arithmetic is correct.

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

@@ -17,11 +17,15 @@ const pence = paddedPenceNumberString
 
 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
+// Step-by-step breakdown:
 // 1. const penceString = "399p": initialises a string variable with the value "399p"
+// 2. penceStringWithoutTrailingP = penceString.substring(0, penceString.length - 1)
+//    Removes the trailing "p", leaving "399"
+// 3. paddedPenceNumberString = "399".padStart(3, "0")
+//    Ensures the string is at least 3 characters long by padding with "0" on the left.
+//    "399" is already 3 chars so it stays "399". For "9p" this would give "009".
+// 4. pounds = paddedPenceNumberString.substring(0, paddedPenceNumberString.length - 2)
+//    Takes all characters except the last 2. For "399" this gives "3" (the pounds part).
+// 5. pence = paddedPenceNumberString.substring(paddedPenceNumberString.length - 2).padEnd(2, "0")
+//    Takes the last 2 characters ("99") as the pence part, and pads to 2 chars if needed.
+// 6. console.log(`£${pounds}.${pence}`): prints "£3.99"