London | 26-ITP-May | Chinwe Chukwuma | Sprint 1 | Module-Structure-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 is performing assignment. It uses the assignment operator = to update the value of count. It evaluates the expression count + 1, then stores the new value back into count.

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 +17,9 @@ 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 lastDotIndex = base.lastIndexOf(".");
+const ext = base.slice(lastDotIndex);
 
 // https://www.google.com/search?q=slice+mdn

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

@@ -4,6 +4,16 @@ 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?
+//num represents a random number between minimum(1) and maximum(100), inclusive.
+
 // Try breaking down the expression and using documentation to explain what it means
+//Math.random() gives a random decimal number between 0 (inclusive) and 1 (exclusive).Example: 0.005, 0.15, 0.999 etc.
+//Math.floor() removes the decimal part and rounds the number down to the nearest whole number. So the value becomes a whole number from 0 and 99.
+//maximum - minimum + 1 gives the range of numbers we want to generate, which is 100 - 1 + 1 = 100. This means we want to generate a random number between 1 and 100, inclusive.
+//Math.random() * (maximum - minimum + 1) gives a random decimal number between 0 (inclusive) and 100 (exclusive).Example: 0.15 * 100 = 15, 0.88 * 100 = 88, 0.999 * 100 = 99.9 etc.
+//Math.floor(Math.random() * (maximum - minimum + 1)) gives a random whole number between 0 (inclusive) and 99 (exclusive). Adding the minimum value shifts this range to between 1 (inclusive) and 100 (inclusive).
+//+ minimum shifts the range of random numbers generated by Math.floor(Math.random() * (maximum - minimum + 1)) from 0-99 to 1-100, inclusive. This makes the final result a whole number between 1 and 100, inclusive.
+
 // 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
+console.log(num);

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?
+We don't want the computer to run these 2 lines - how can we solve this problem?
+
+//We can comment it out to stop the computer from executing it by using either // for single-line comment or /* */ for multi-line comment.

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

@@ -2,3 +2,7 @@
 
 const age = 33;
 age = age + 1;
+
+/*This threw the error TypeError: Assignment to constant variable because the line
+ age = age + 1 attempts to change the value of age after a constant variable is created.
+ Constant variables cannot be reassigned after initial value is set.*/

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

@@ -3,3 +3,12 @@
 
 console.log(`I was born in ${cityOfBirth}`);
 const cityOfBirth = "Bolton";
+
+/* ReferenceError: Cannot access 'cityOfBirth' before initialisation occured because cityOfBirth is used before it is declared. 
+JavaScript executes code from top to bottom, and the console.log tries to access cityOfBirth before the const cityOfBirth = "Bolton"; line has run.
+Variables declared with const cannot be accessed before their declaration, so JavaScript throws a ReferenceError. 
+To fix this error, move the declaration above the console.log
+Like this:
+const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);
+*/

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

@@ -1,9 +1,19 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
+//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
+/* I predict that the code will fail because cardNumber is a number, and numbers do not have a .slice() method.
+.slice() only workon strings and arrays. Since JavaScript cannot call .slice() on a number, it will throw a TypeError.  */                                                                     
+
 // Then run the code and see what error it gives.
+// It gives TypeError: cardNumber.slice is not a function.
+
 // Consider: Why does it give this error? Is this what I predicted? If not, what's different?
+//JavaScript throws the TypeError because numbers do not have the.slice() method and therefore cannot be sliced and cardNumber is a number.
+
 // Then try updating the expression last4Digits is assigned to, in order to get the correct value
+const last4Digits = String(cardNumber).slice(-4);
+console.log(last4Digits);

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

@@ -1,2 +1,5 @@
 const 12HourClockTime = "8:53pm";
 const 24hourClockTime = "20:53";
+
+//JavaScript throws a SyntaxError: Invalid or unexpected token because it does not allow variables to start with a number.
+// The variable 12HourClockTime starts with a number 12 making the entire identifier invalid therefore JavaScript could not interpret the variable as valid syntax.

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

@@ -12,11 +12,40 @@ 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 calls in the file. Function call is when parentheses is added to its name: name().
+/* The Lines where function call is made:
+ replaceAll(",","") which appear twice in both line 4 carPrice.replaceAll(",", "") and
+ line 5 priceAfterOneYear.replaceAll("," "").
+
+ Number(...) which appears twice aswell:
+ Also in line 4 Number(carPrice.replaceAll(",", "")) and line 5 Number(priceAfterOneYear.replaceAll("," ""))
+
+ console.log(...) in line 10
+ console.log(`The percentage change is ${percentageChange}`)
+ */
+
 
 // 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 is in line 5.It throws the error SyntaxError: missing ) after argument list because it 
+is expecting a comma between the arguments in replaceAll(",", "") but sees this replaceAll(","  "").
+To fix it you just add the missing comma.*/
 
 // c) Identify all the lines that are variable reassignment statements
+/*  Line 4 and 5 are the variable reassignment statements.
+carPrice = Number(carPrice.replaceAll(",", ""));
+priceAfterOneYear = Number(priceAfterOneYear.replaceAll("," ""));
+*/
 
 // d) Identify all the lines that are variable declarations
+/* Lines 1,2,7 and 8 are variable declarations.
+let carPrice = "10,000";
+let priceAfterOneYear = "8,543";
+
+const priceDifference = carPrice - priceAfterOneYear;
+const percentageChange = (priceDifference / carPrice) * 100;
+*/
 
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+/* The expression first uses replaceAll(",","") to remove all commas from the string "10,000" turning it into "10000". Then the Number(...) converts that string into the actual number.
+The purpose is to convert a price written as string with commas into a real number so mathematical calculations can be performed.
+*/

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

@@ -12,14 +12,33 @@ 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 declarations.
+const movieLength 
+const remainingSeconds 
+const totalMinutes 
+const remainingMinutes
+const totalHours 
+const result */
 
 // b) How many function calls are there?
+// one 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
+/* movieLenth % 60 means: Divide movieLength by 60 and return the leftover seconds.
+Example: 8784 / 60 = 146 minutes, remainder 24 seconds. Which makes remainingSeconds = 24.*/
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+/* line 4 is calculating the total number of whole minutes in the movie. It removes the leftover seconds (remainingSeconds=24) from movieLength (8784),
+ leaving only the seconds that form complete minutes.
+Dividing that value by 60 converts those full seconds into whole minutes. So tottalMinutes = 146.
 
 // 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
+// result represents formatted time string so the better name will be formattedTime.
+
+// f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer.
+/* It works correctly with positive values, but breaks or becomes weird when:
+negative number is used because time cannot be negative.
+numbers less than 60 is used results in zero hour and minutes.
+non-integer values are used, remainder logic becomes messy.
+extremely large numbers are used, it works but formatting becomes unrealistic. */

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

@@ -25,3 +25,23 @@ console.log(`£${pounds}.${pence}`);
 
 // To begin, we can start with
 // 1. const penceString = "399p": initialises a string variable with the value "399p"
+
+/* 2. const penceStringWithoutTrailingP = penceString.substring(
+  0,
+  penceString.length - 1
+): Removes the trailing "p" from the original String, leaving only the numeric part. It takes a substring starting at index 0 and ending just before the last Character, so "399p" becomes "399".
+
+3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0"): Ensures the pence value is at least three characters long by padding with leading zero if necessary. Eg, "3" would become "003", "99" would become "099" while "399" remains "399".
+
+4. const pounds = paddedPenceNumberString.substring(
+  0,
+  paddedPenceNumberString.length - 2
+): Extracts the pounds portion from the padded string by taking all characters except the last two, making "399" be "3" representing the pounds component.
+
+5.const pence = paddedPenceNumberString
+  .substring(paddedPenceNumberString.length - 2)
+  .padEnd(2, "0"): Extracts the last two characters as the pence portion and ensures it is exactly two digits by padding with trailing zeros if needed. "399" becomes "99", representing the pence component.
+
+  6. console.log(`£${pounds}.${pence}`): Outputs the final formatted price in pounds and pence. Eg, £3.99.
+
+*/

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

@@ -11,8 +11,12 @@ In the Chrome console,
 invoke the function `alert` with an input string of `"Hello world!"`;
 
 What effect does calling the `alert` function have?
+Calling alert("Hello World!") displays a pop-up message box containing the text "Hello World!". The user will now have to click OK to dismiss it.
 
 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`.
 
 What effect does calling the `prompt` function have?
+Calling prompt("What is your name?") displays a pop-up box with a text input feild. The user can type a response, and the gunction returns whatever text the user entered. If the user clicks Cancel, the return value is null.
+
 What is the return value of `prompt`?
+The return value is the text the user typed, or null if the cancelled.

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

@@ -5,12 +5,21 @@ 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?
+It outputs: f log() {[native code]}
 
 Now enter just `console` in the Console, what output do you get back?
+It outputs: console {debug: f, error: f, info: f, log: f, warn: f, ...}
 
-Try also entering `typeof console`
+Try also entering `typeof console`: This outputs: 'object'
 
 Answer the following questions:
 
 What does `console` store?
+console stores a collection of functions that allows outputting of information, display warnings, show errors, and interact with the browser's debugging tools. Eg: console.log, console.debug, console.assert,etc
+
 What does the syntax `console.log` or `console.assert` mean? In particular, what does the `.` mean?
+The . is the dot operator, and it is used to access a property or method inside an object.
+So:
+console.log means "access the log function inside the console object".
+
+console.assert means "access the assert function inside the console object".