London | 26-ITP-Sep | Hanna Bohlin | Sprint 2 | Sprint 2 coursework

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

@@ -4,3 +4,7 @@ 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
+
+// Answer: The = is an assignment operator (as opposed to == and === which are comparison operators).
+// In line 3, a new value is assigned to the variable count. This is allowed because the variable was
+// declared using let. count is reassigned to the old value of count plus 1.

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

@@ -5,6 +5,8 @@ const 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.
 
-const initials = ``;
+const initials = `${firstName.charAt(0)}${middleName.charAt(0)}${lastName.charAt(0)}`;
+
+console.log(initials);
 
 // https://www.google.com/search?q=get+first+character+of+string+mdn

Sprint-2/1-key-exercises/3-paths.js

@@ -17,7 +17,11 @@ 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);
+console.log(`The dir part of ${filePath} is ${dir}`);
 
-// https://www.google.com/search?q=slice+mdn
+const lastPeriodIndex = filePath.lastIndexOf(".");
+const ext = filePath.slice(lastPeriodIndex);
+console.log(`The ext part of ${filePath} is ${ext}`);
+
+// https://www.google.com/search?q=slice+mdn

Sprint-2/1-key-exercises/4-random.js

@@ -7,3 +7,20 @@ 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
+
+console.log(num);
+
+// Answer: num is a random number between 1 and 100, including 1 and 100. So if I change the values of minimum
+// and maximum it will be a random value between them, including them.
+
+// Math.random generates a random value between 0 and 1, including 0 but not 1.
+
+// (maximum - minimum + 1) gives the amounts of values we want to be able to generate.
+// If minimum was 60 and maximum was 70, inclusive, that would make 11 possible values
+
+// Math.random * (maximum - minimum + 1) would generate any value between 0 and 11, including 0 but not 11
+
+// Math.floor rounds the value down, leaving us with any value between 0 and 10 inclusive
+
+// + minimum at the end, 60 in our thought experiment, makes the values range between 60 and 70 inclusive
+// which is what we wanted.

Sprint-2/2-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?
+
+// Answer: I turned the lines into comments, now they won't run

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

@@ -1,4 +1,8 @@
 // trying to create an age variable and then reassign the value by 1
 
-const age = 33;
+let age = 33;
 age = age + 1;
+
+// Answer: I got the error message TypeError: Assignment to constant variable.
+// That is because age was declared using const, which makes it non-reassignable.
+// I changed the const to let, so the variable age becomes reassignable

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

@@ -1,5 +1,9 @@
 // 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}`);
 const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);
+
+// Answer: I got the error message ReferenceError: Cannot access 'cityOfBirth' before initialization
+// This is because the program tries to access cityOfBirth before it has been initialized.
+// I switched the lines around, so cityOfBirth gets declared before it is referenced.

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

@@ -1,9 +1,23 @@
 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: I believe slice counts forward from the start when you use positive values, and
+// backwards from the end when you use negative. So if you only put in one negative number, it's counts
+// backward from the end to the last 4, but can't "turn around" to count up to the end again..?
+
+// After running the code: The actual error was a TypeError, saying that cardNumber.slice is not a function.
+// That means you can't put anything in parenthesis after cardNumber.slice. However, when I used slice before
+// slice definitely takes parameters. This made me think about the fact that cardNumber is actually a
+// number, and slice is probably only for strings or arrays. You can't really count positions in a number.
+
+// I solved it by chaining a toString before slicing. My initial theory was completely wrong, putting a
+// negative number in slice is completely fine. Now last4Digits is a string, not a number. But it seems
+// easier to work with as a string, if specific digits need to be accessed, so I will keep it as a string.

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

@@ -1,2 +1,6 @@
-const 12HourClockTime = "8:53pm";
-const 24hourClockTime = "20:53";
+const twelveHourClockTime = "8:53pm";
+const twentyfourHourClockTime = "20:53";
+
+// Answer: I got the error message SyntaxError: Invalid or unexpected token
+// There were arrows pointing at "12" in 12HourClockTime. That is because
+// variable names cannot start with numbers in javascript. I changed them to start with letters.

Sprint-2/3-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 +13,30 @@ 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
 
+// 5 function calls are made.
+// Line 4 calls function replaceAll and Number
+// Line 5 calls functions replaceAll and Number
+// Line 10 calls 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?
 
+// There is a syntax error. The error says a closing parenthesis is missing, which I think is triggered
+// because a comma in the argument list is missing. I added the comma and the error is resolved.
+
 // c) Identify all the lines that are variable reassignment statements
 
+// Line 4 reassigning carPrice
+// Line 5 reassigning priceAfterOneYear
+
 // d) Identify all the lines that are variable declarations
 
+// Line 1 declares carPrice with let
+// Line 2 declares priceAfterOneYear with let
+// Line 7 declares priceDifference with const
+// Line 8 declares percentageChange with const
+
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+
+// The original carPrice is a string. In order to do math and get a percentage the string needs to be converted
+// into a number first. And before that the string's comma needs to be removed (it's replaced with nothing
+// using replaceAll)

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

@@ -1,4 +1,4 @@
-const movieLength = 8784; // length of movie in seconds
+const movieLength = 145678; // length of movie in seconds
 
 const remainingSeconds = movieLength % 60;
 const totalMinutes = (movieLength - remainingSeconds) / 60;
@@ -13,13 +13,33 @@ console.log(result);
 
 // a) How many variable declarations are there in this program?
 
+// 6
+
 // b) How many function calls are there?
 
+// 1, console.log(result) on line 10
+
 // 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 arithmetic operator. The expression gives the remainder after the number of seconds
+// the movie is long is divided by 60. After you have the full amount of minutes this is the amount of
+// remaining seconds that don't add up to a full minute.
+
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
 
+// removing remainingSeconds from movieLength leaves a number of seconds, slightly shorter than the movie length,
+// that are an exact amount of minutes. It is divisible by 60. Dividing that number by 60 gives the exact
+// number of minutes.
+
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
 
+// It represents the movie length as a string expressed in hours, minutes and seconds. A different name could
+// be moiveLengthDestructured, movieLengthMessage, movieLengthInHMS, movieLengthFormatted, movieLengthTimeFormat
+
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+
+// It technically works for all movie lengths, but the format gets weird. when a value is a single digit, you
+// would expect 05 or 00, but it just says 5 or 0 which isn't a standard way to show time. Also, when the
+// hours go above 24 you would expect it to start counting days, but the hours just add up instead as
+// you try higher values.

Sprint-2/3-mandatory-interpret/3-to-pounds.js

@@ -2,13 +2,14 @@ const penceString = "399p";
 
 const penceStringWithoutTrailingP = penceString.substring(
   0,
-  penceString.length - 1
+  penceString.length - 1,
 );
 
 const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+
 const pounds = paddedPenceNumberString.substring(
   0,
-  paddedPenceNumberString.length - 2
+  paddedPenceNumberString.length - 2,
 );
 
 const pence = paddedPenceNumberString
@@ -25,3 +26,41 @@ console.log(`£${pounds}.${pence}`);
 
 // To begin, we can start with
 // 1. const penceString = "399p": initialises a string variable with the value "399p"
+
+// Answers
+
+// 2. const penceStringWithoutTrailingP = penceString.substring(
+//    0,
+//    penceString.length - 1
+//    );
+// This declares and initialises a new variable penceStringWithoutTrailingP that is a substring of
+// penceString, starting at position 0 and up to but not including the last position. So the new variable
+// gets the value "399", the p is left behind.
+
+// 3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+// We now want our value to be at least 3 digits long, but in case it is shorter, we want to fill up with zeros at
+// the start so it becomes 3 digits long. padStart does that, the 3 specifies minimum amount of digits and the "0"
+// specifies what to fill with. The result gets saved in new variable paddedPenceNumberString.
+
+// 4. const pounds = paddedPenceNumberString.substring(
+//      0,
+//      paddedPenceNumberString.length - 2
+//    );
+// Now we save the pounds amount into new variable pounds. We get the amount (which could be any amount of digits long)
+// by creating a substring from paddedPenceNumberString starting at position 0 and ending before the next to
+// last digit. The last two digits are the pence amount and they aren't included in pounds.
+
+// 5. const pence = paddedPenceNumberString
+//      .substring(paddedPenceNumberString.length - 2)
+//      .padEnd(2, "0");
+// Similarly to the previous operation, here we save the pence amount into new variable pence. We get it by
+// using substring on paddedPenceNumberString again, this time starting two digits from the end, saving the
+// final two digits into pence. Then, if the digits are fewer than 2, we chain a padEnd to add "0" until pence
+// is 2 digits long.
+// After trying different values, it seems like it is unnecessary to have the padEnd, since the pence will
+// always already be 2 digits long. Even if penceString started with just 1 digit, "0"s will have been padded
+// earlier at the beginning of the string, so pence can always be 2 digits and the padEnd will never take effect.
+
+// 6. console.log(`£${pounds}.${pence}`);
+// Using a template literal, here we log the £ sign followed by the the pounds amount, a period and the pence
+// amount, which is formatted to understand easier than the original penceString was.

Sprint-2/4-stretch-explore/chrome.md

@@ -9,7 +9,14 @@ In the Chrome console, invoke the function `alert` with one argument, the string
 
 What effect does calling the `alert` function have?
 
+Answer: An alert popped up
+
 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?
+
+Answer: A poppup prompts me to write my name.
+
 What is the return value of `prompt`?
+
+Answer: The value I entered in the text box.

Sprint-2/4-stretch-explore/objects.md

@@ -6,11 +6,23 @@ Open the Chrome devtools Console, type in `console.log` and then hit enter
 
 What output do you get?
 
+Answer: f log() { [native code] }
+
 Now enter just `console` in the Console, what output do you get back?
 
+Answer: console {debug: ƒ, error: ƒ, info: ƒ, log: ƒ, warn: ƒ, …}
+
 Try also entering `typeof console`
 
+Answer: it's an 'object' !!!
+
 Answer the following questions:
 
 What does `console` store?
+
+Answer: A console object with loads of console functions (methods)?
+
 What does the syntax `console.log` or `console.assert` mean? In particular, what does the `.` mean?
+
+Answer: I think the period means it's a method call, for console object methods. and log and assert are the
+methods.