NW | 25-ITP-Sep | TzeMing Ho | Sprint 1 | coursework/sprint-1

.gitignore

@@ -1,4 +1,6 @@
 node_modules
 .DS_Store
 .vscode
-**/.DS_Store
+**/.DS_Store
+package-lock.json
+.env

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 reassigning the count value to be the current value of count plus 1, which is also a statement.

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]}`;
+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 +17,9 @@ 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 ext = base.slice(base.lastIndexOf("."));
+console.log(`The dir part of ${filePath} is ${dir}`);
+console.log(`The ext part of ${filePath} is ${ext}`);
 
 // https://www.google.com/search?q=slice+mdn

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

@@ -7,3 +7,10 @@ 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.floor - Rounds a number DOWN to the nearest integer
+// Math.random - generates a random floating number > 0 and < 1
+// (maximum - minimum + 1) = 100 - 1 + 1 = 100
+// So, num represents a rounded down random integer generated between 1 and 100
+// Edge case: Math.floor(99.99) + 1 = 99 + 1 = 100
+console.log(num);

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?
+// We can comment them out

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

@@ -1,4 +1,4 @@
 // trying to create an age variable and then reassign the value by 1
 
-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 ?
+// The variable should be declared before it is used in console.log
 
-console.log(`I was born in ${cityOfBirth}`);
 const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);

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

@@ -1,5 +1,9 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
+const last4Digits = String(cardNumber).slice(-4);
+
+// A number was not able to be sliced, whereas a string can be sliced
+// So, the error is that cardNumber should be a string, not a number
+console.log(last4Digits);
 
 // The last4Digits variable should store the last 4 digits of cardNumber
 // However, the code isn't working

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

@@ -1,2 +1,4 @@
-const 12HourClockTime = "20:53";
-const 24hourClockTime = "08:53";
+const twelveHourClockTime = "20:53";
+const twentyFourHourClockTime = "08:53";
+
+// Change the above names of variables to avoid errors

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;
@@ -13,10 +13,27 @@ console.log(`The percentage change is ${percentageChange}`);
 
 // 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 this file
+// Line 4: carPrice.replaceAll(",", "")
+// Line 4: Number(carPrice.replaceAll(",", ""))
+// Line 5: priceAfterOneYear.replaceAll("," "")
+// Line 5: Number(priceAfterOneYear.replaceAll("," ""))
+// Line 8: 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 coming from line 5
+// The error is due to a missing comma
+// Add a comma between the two quotations
+
 // c) Identify all the lines that are variable reassignment statements
 
+// Line 4 and Line 5
+
 // d) Identify all the lines that are variable declarations
 
+// Line 1, Line 2, Line 7 and Line 8
+
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+
+// The expression is replacing all the commas in the string carPrice with nothing, and then converting it to a number type

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

@@ -8,18 +8,37 @@ const totalHours = (totalMinutes - remainingMinutes) / 60;
 
 const result = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
 console.log(result);
+console.log(remainingSeconds)
 
 // 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 variable declarations
+
 // b) How many function calls are there?
 
+    // There is 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 a remainder operator.
+    // movieLength % 60 represents the remainder when 8784/60 is calculated, which is 24 seconds
+
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
 
+    // The expression is calculating the total number of minutes in the movie length
+    // It does this by subtracting the remaining seconds from the total movie length, and then dividing it by 60
+
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
 
+    // The result represents the movie length in hours:minutes:seconds
+    // A better name could be hoursMinutesSeconds or movieLengthFormatted
+
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+
+    // The code will only work for positive integers
+    // if the value is 0 or negative, the code will not make sense
+    // if the value is a decimal, the code will give float results
+    // if the value is not a number, the code will give an error

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

@@ -25,3 +25,27 @@ 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): 
+//    2.1 removes the trailing 'p' from the string by taking a substring from index 0 to the second last character
+//    2.2 penceStringWithoutTrailingP now = "399"
+
+// 3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0"):
+//    3.1 ensures the string has at least 3 characters by adding zeros to the start if necessary
+//    3.2 However, since "399" already has 3 characters, it remains unchanged
+//    3.3 paddedPenceNumberString now = "399"
+
+// 4. const pounds = paddedPenceNumberString.substring(0, paddedPenceNumberString.length - 2):
+//    4.1 taking the first characters of the string up to the last two characters
+//    4.2 since "399" has only 3 characters, this only takes the first character
+//    4.3 pounds now = "3"
+
+// 5. const pence = paddedPenceNumberString.substring(paddedPenceNumberString.length - 2).padEnd(2, "0"):
+//    5.1 takes the last two characters of the string to represent the pence
+//    5.2 since "399" has only 3 characters, this takes the last two characters "99"
+//    5.3 padEnd(2, "0") ensures that if there were less than 2 characters, it would add a "0" to the end
+//    5.4 pence now = "99"
+
+// 6. console.log(`£${pounds}.${pence}`):
+//    6.1 constructs a formatted string representing the price in pounds and pence
+//    6.2 prints "£3.99" to the console

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

@@ -11,8 +11,13 @@ In the Chrome console,
 invoke the function `alert` with an input string of `"Hello world!"`;
 
 What effect does calling the `alert` function have?
+The alert function call a small separate window pop out, written "Hello world!". There is a OK button at the bottom right 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?
+The prompt function pop out a small window similar to alert but it has a input section where I can type my name.
+
 What is the return value of `prompt`?
+The return value of prompt is a string. If we did not enter anything and pressed ok, the value is also a string.
+However, if we pressed cancel, it will return null.

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

@@ -5,12 +5,22 @@ 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?
+I got ƒ log() { [native code] }
+Chrome is telling me console.log a built-in function.
 
 Now enter just `console` in the Console, what output do you get back?
+The output is the console object, which has many built-in methods, such as assert, clear, and context.
 
 Try also entering `typeof console`
+The type of console is an object.
 
 Answer the following questions:
 
 What does `console` store?
+A console contains its properties, and many of its properties are built-in methods that we can call.
+
 What does the syntax `console.log` or `console.assert` mean? In particular, what does the `.` mean?
+The syntax console.log references to the log method built-in the console object, whereas console.assert references to the assert method.
+The log method can output message to the console.
+The assert method can output a error message when an assertion is false.
+In particular, the "." is a accessing method syntax. As a console is an object which has many built-in methods, the "." can refer to the corresponding method after the ".", such as log and assert.