London | May-2025 | Reza Jahanimir | Sprint-1

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

@@ -4,3 +4,6 @@ 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
+
+// We are updating the previous value of count to a new value. The = operator assigns a new value 
+// to the variable, meaning the data stored in memory is being changed.

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

@@ -5,7 +5,8 @@ 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
 
+console.log(initials);

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

@@ -9,15 +9,13 @@
 
 // (All spaces in the "" line should be ignored. They are purely for formatting.)
 
-const filePath = "/Users/mitch/cyf/Module-JS1/week-1/interpret/file.txt";
 const lastSlashIndex = filePath.lastIndexOf("/");
-const base = filePath.slice(lastSlashIndex + 1);
-console.log(`The base part of ${filePath} is ${base}`);
+const lastDotIndex = filePath.lastIndexOf(".");
 
-// Create a variable to store the dir part of the filePath variable
-// Create a variable to store the ext part of the variable
+const base = filePath.slice(lastSlashIndex + 1);   // file.txt
+const dir = filePath.slice(0, lastSlashIndex);     // /Users/mitch/cyf/Module-JS1/week-1/interpret
+const ext = filePath.slice(lastDotIndex);          // .txt
 
-const dir = ;
-const ext = ;
-
-// https://www.google.com/search?q=slice+mdn
+console.log(`Base part of path: ${base}`);
+console.log(`Dir part of path: ${dir}`);
+console.log(`Ext part of path: ${ext}`);

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

@@ -3,7 +3,25 @@ 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
+
+
+// order of math calculation - () > ** > * / % > + - (Parentheses first, then Exponentiation 
+// (right to left), then Multiplication/Division/Modulo (left to right), then Addition/Subtraction 
+// (left to right)).
+
+//Math.floor - returns the value of x rounded down to its nearest integer
+//Math.random - returns a random number 
+
+// First, the innermost parentheses are evaluated: (maximum - minimum + 1).
+// Then, the result is multiplied by the random number generated by the Math object.
+// Math.floor rounds the result down to the nearest integer.
+// Finally, the value is added to the minimum.
+
+// the purpose  - To generate a random whole number between minimum and maximum, inclusive.
+// output - It will be a random integer between 1 and 100.

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

@@ -1,2 +1,4 @@
-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?
+
+//we sole this by witting these two as comments 

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;
+
+// we have to use let as it allows the value to be reassign

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

@@ -1,5 +1,15 @@
 // 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}`);
+// the system reads the code top to bottom and because the variable has been create/define before 
+// the consol.log it can not recognize the variable
+
+//Wrong
+//console.log(`I was born in ${cityOfBirth}`);
+//const cityOfBirth = "Bolton";
+
+//correct
 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
+// result as a string
+let cardNumber = 4533787178994213;
+const last4Digits = cardNumber.toString().slice(-4);
+console.log(last4Digits); // Output: "4213"
+
+
+// result as a number
+const last4DigitsNum = Number(cardNumber.toString().slice(-4));
+console.log(last4DigitsNum); // Output: 4213
+
+
+// the function your asked return string
+function last4DigitsStr(cardNumber) {
+  const last4Digs= cardNumber.toString().slice(-4);
+  return last4Digs;
+}
+
+// the function your asked return number
+function last4DigitsNum(number) {
+  const last4Digs= Number(number.toString().slice(-4));
+  return last4Digs;
+}

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

@@ -1,2 +1,15 @@
-const 12HourClockTime = "20:53";
-const 24hourClockTime = "08:53";
+const HourClockTime24 = "20:53";
+const hourClockTime12 = "08:53";
+
+// Go Variable Naming Rules
+// A variable can have a short name (like x and y) or a more descriptive name (age, price, carname, etc.).
+
+// Go variable naming rules:
+
+// A variable name must start with a letter or an underscore character (_)
+// A variable name cannot start with a digit
+// A variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ )
+// Variable names are case-sensitive (age, Age and AGE are three different variables)
+// There is no limit on the length of the variable name
+// A variable name cannot contain spaces
+// The variable name cannot be any Go keywords

Sprint-1/3-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 +12,42 @@ 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: 
+// Line 4 - .replaceAll, Number
+// Line 5 - .replaceAll, 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?
+// from line :5
+// fix: add , - priceAfterOneYear = Number(priceAfterOneYear.replaceAll(",", ""));
+// Why is the original line causing an error?
+// We were trying to subtract two string values like "30000" - "24000" but 
+// In JavaScript, strings with commas (like "24,000") can’t be parsed directly to numbers 
+// So this fails
+
+
 
 // c) Identify all the lines that are variable reassignment statements
+// line  4 , 5
+
+
 
 // d) Identify all the lines that are variable declarations
+// lines : 1 , 2 , 7 , 8
+// Line 1: let carPrice
+// Line 2: let priceAfterOneYear
+// Line 6: const priceDifference
+// Line 7: const percentageChange
+
+
 
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+// method replaceAll is changing a specific character and replace it with the one we asked for. 
+// function number which changes a string number value to integers.
+// purpose : is to have a integer instead of a string 
+
+// explain why we want to convert it into an integer?
+// We use Number(carPrice.replaceAll(",", "")) to convert a formatted string into a real number, 
+// so we can do mathematical calculations on it.

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

@@ -6,20 +6,32 @@ const totalMinutes = (movieLength - remainingSeconds) / 60;
 const remainingMinutes = totalMinutes % 60;
 const totalHours = (totalMinutes - remainingMinutes) / 60;
 
-const result = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
-console.log(result);
+const formattedTime = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
+console.log(totalMinutes);
 
 // 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?
+// 6
 
 // b) How many function calls are there?
+// 1 
 
 // 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 (modulo) returns the remainder of a division. 
+// In this case, it returns how many seconds are left after dividing the total seconds by 60.
+// For example, 8784 % 60 = 24 — so 24 seconds remain.
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// we are calculating the total minutes. 
+// we subtract movieLength by remainingSeconds because remaining seconds don't add up to a full min.
+// convert to minute by dividing by 60.
 
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
-
+// The variable `result` represents the movie's length in a time format: `HH:MM:SS`. 
+// string format 
+// better name can be `formattedTime` or `HHMMSS`
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+// Yes, the code works for all non-negative values of `movieLength`, including 0.
+// However, for values less than 60, it will return 0 hours and 0 minutes

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

@@ -24,4 +24,23 @@ console.log(`£${pounds}.${pence}`);
 // 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"
+// 1. const penceString = "399p": initializes a string variable with the value "399p"
+
+// 2. const penceStringWithoutTrailingP = penceString.substring(0, penceString.length - 1);
+// .substring - selects a section between the given indexes in a string -> "399", by doing this we remove the "p"
+
+// 3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+// The padStart() method pads penceStringWithoutTrailingP with another string (multiple times) until it reaches a given length 3.
+// id we have a one digit number it adds two "004" but if the number is 3 digits will keep it as it is "399"
+
+// 4. const pounds = paddedPenceNumberString.substring(0, paddedPenceNumberString.length - 2);
+// Extracts the pound portion, which is the first part of the 3-digit string -> "3"
+
+// 5. const pence = paddedPenceNumberString
+// .substring(paddedPenceNumberString.length - 2)
+// .padEnd(2, "0");
+// it is two separate parts
+// first - with substring method we select the two last digits
+// second - ensures that if somehow only one digit is returned it’s padded to two characters by adding a "0" to the end.
+
+// 6. Displays the formatted price in British pounds -> £3.99 or £0.05

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

@@ -11,8 +11,18 @@ In the Chrome console,
 invoke the function `alert` with an input string of `"Hello world!"`;
 
 What effect does calling the `alert` function have?
+    -It causes the browser to display a modal popup box with the message "Hello world!"
+    -It blocks interaction with the page until the user clicks "OK"
+    -It returns undefined — the purpose is only to notify, not to receive input.
 
 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`.
+const myName = prompt("What is your name?");
+
 
 What effect does calling the `prompt` function have?
+browser displays a popup dialog box
+
 What is the return value of `prompt`?
+    A string - if the user types something and clicks OK
+    An empty string ("") - if they click OK but type nothing
+    null - if the user clicks Cancel

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

@@ -5,12 +5,30 @@ In this activity, we'll explore some additional concepts that you'll encounter i
 Open the Chrome devtools Console, type in `console.log` and then hit enter
 
 What output do you get?
+ƒ log() { [native code] }
+
 
 Now enter just `console` in the Console, what output do you get back?
+console {debug: ƒ, error: ƒ, info: ƒ, log: ƒ, warn: ƒ, …}
 
 Try also entering `typeof console`
+typeof(console);
+'object'
 
 Answer the following questions:
 
 What does `console` store?
+console is a built-in JavaScript object provided by browsers (like Chrome, Firefox, etc.). It stores a collection of functions that help developers log, debug, and inspect values during runtime.
+It doesn’t store data like a variable; instead, it holds methods (a.k.a. functions) like:
+console.log() – print to the console
+console.error() – print errors
+console.warn() – print warnings
+console.assert() – test if an expression is true
+
 What does the syntax `console.log` or `console.assert` mean? In particular, what does the `.` mean?
+- `console.log` or `console.assert`
+These are method calls on the console object.
+You're telling JavaScript: "Use the log or assert method that belongs to the console object."
+- the `.` mean
+The dot (.) is the member access operator in JavaScript.
+It accesses a property or method of an object