London | 26-ITP-January | Laura C | Sprint 1 | Structuring and Testing Data

Sprint-1/1-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 updates the value of count.
+// The = means “set count to a new value”, which is the old value plus 1.

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];
+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 +17,10 @@ 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
+console.log(dir);
+console.log(ext);
+
+// https://www.google.com/search?q=slice+mdn

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

@@ -7,3 +7,23 @@ const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
 // 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
+
+// Math.random() generates a random decimal number between 0 - inclusive and 1 (exclusive)
+const randomDecimal = Math.random();
+console.log("randomDecimal:", randomDecimal);
+// Calculate how many numbers are in the range between minimum and maximum (inclusive)
+const range = maximum - minimum + 1;
+console.log("range:", range);
+// Scale the random decimal to fit within the range...
+const scaledNumber = randomDecimal * range;
+console.log("scaledNumber:", scaledNumber);
+// Round the scaled number down to the nearest whole number
+const wholeNumber = Math.floor(scaledNumber);
+console.log("wholeNumber:", wholeNumber);
+// Shift the number so it starts from the minimum value...
+const finalNumber = wholeNumber + minimum;
+console.log("finalNumber:", finalNumber);
+
+// The variable num is a random whole number between minimum and maximum - inclusive
+console.log("num:", num);
+

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

@@ -1,2 +1,2 @@
-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?

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

@@ -1,4 +1,6 @@
 // trying to create an age variable and then reassign the value by 1
 
-const age = 33;
+let age = 33;
 age = age + 1;
+console.log(age);
+

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 ?
+// The error is caused by using the variable before it is declared
+// and by using single quotes instead of backticks for a template string
 
-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 +1,18 @@
 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
+
+// Prediction:
+// cardNumber is a number, not a string
+// The slice method only works on strings (and arrays)
+// So calling slice on a number will cause an error
+

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

@@ -1,2 +1,5 @@
-const 12HourClockTime = "20:53";
-const 24hourClockTime = "08:53";
+// The error occurs because variable names cannot start with numbers
+// JavaScript identifiers must begin with a letter, $ or _
+
+const twelveHourClockTime = "20:53";
+const twentyFourHourClockTime = "08:53";

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

@@ -2,21 +2,43 @@ 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) How many function calls are there in this file? Write down all the lines where a function call is made
+// Function calls are when we use () like: something()
+// Line 4: carPrice.replaceAll(",", "")
+// Line 4: Number(...)
+// Line 5: priceAfterOneYear.replaceAll(",", "")
+// Line 5: Number(...)
+// Line 10: console.log(...)
+// Answer: 5 function calls
 
 // 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 comes from the console.log line because it uses single quotes with ${percentageChange}
+// ${...} only works inside backticks `...` (template strings)
+// Fix: use backticks: console.log(`The percentage change is ${percentageChange}`);
 
 // c) Identify all the lines that are variable reassignment statements
+// Reassignment means we change an existing variable's value (no let/const on the line)
+// Line 4: carPrice = Number(carPrice.replaceAll(",", ""));
+// Line 5: priceAfterOneYear = Number(priceAfterOneYear.replaceAll(",", ""));
+// Answer: I think lines 4 and 5
 
 // d) Identify all the lines that are variable declarations
+// Declarations use let or const
+// 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;
+// Answer: lines 1, 2, 7 and 8
+
+// e) Describe what the expression Number(carPrice.replaceAll(",", "")) is doing - what is the purpose of this expression?
+// replaceAll(",", "") removes commas from the string (e.g. "10,000" becomes "10000")
+// Number(...) converts the cleaned string into a real number so we can do maths with it
+// Purpose: turn "10,000" (text) into 10000 (number)
 
-// e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?

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

@@ -9,17 +9,40 @@ 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) How many variable declarations are there in this program?
+// Declarations are lines that use const or let
+// const movieLength
+// const remainingSeconds
+// const totalMinutes
+// const remainingMinutes
+// const totalHours
+// const result
+// My answer: 6 variable declarations
 
 // b) How many function calls are there?
+// A function call uses parentheses like something(..)
+// console.log(result) is a function call
+// My answer: 1 function call
 
 // c) Using documentation, explain what the expression movieLength % 60 represents
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
+// % is the remainder operator
+// movieLength % 60 gives the leftover seconds after dividing by 60
+// (the seconds part that doesn't make a full minute)
+// Answer: it represents the remaining seconds
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// totalMinutes = (movieLength - remainingSeconds) / 60
+// First it removes the leftover seconds so we have an exact number of seconds that fits into whole minutes
+// Then it divides by 60 to convert seconds into minutes
+// Answer: it calculates the total whole minutes in the movie
 
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
+// result is a string that formats the time as hours:minutes:seconds
+// Better name: formattedTime or movieDuration
 
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+// It works for normal positive numbers (seconds) like 8784
+// It will also run for 0 (gives 0:0:0)
+// But negative values would produce negative hours/minutes/seconds, which isn't a real time format
+// So it assumes movieLength is a non-negative number
+

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

@@ -25,3 +25,56 @@ console.log(`£${pounds}.${pence}`);
 
 // To begin, we can start with
 // 1. const penceString = "399p": initialises a string variable with the value "399p"
+
+// creates a string that represents a price in pence, including the letter "p"
+//
+// Example: "399p"
+//
+// This is the original input value we want to convert into pounds.
+
+
+// 2. const penceStringWithoutTrailingP = ...
+// Uses substring to remove the last character ("p") from the string
+//
+// We take the string from index 0 up to (but not including) the last character
+//
+// Result: "399"
+//
+// This leaves us with only the numeric part of the price as a string.
+
+
+// 3. const paddedPenceNumberString = ...
+// padStart ensures the string is at least 3 characters long
+//
+// This is important for small values like "5p":
+// "5" becomes "005"
+//
+// Result for "399": "399"
+// Result for "5p": "005"
+
+
+// 4. const pounds = ...
+// Extracts all characters except the last two
+//
+// The last two characters represent pence,
+// everything before that represents pounds
+//
+// For "399":
+// pounds = "3"
+
+
+// 5. const pence = ...
+// Takes the last two characters of the string
+//
+// padEnd ensures the pence value is always two digits
+//
+// For "399":
+// pence = "99"
+
+
+// 6. console.log(`£${pounds}.${pence}`)
+// Combines pounds and pence into a formatted price string
+//
+// Final output:
+// £3.99
+