West Midlands | ITP Sept 25 | Georgina Rogers | Sprint 1 | Structuring and Testing Data

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 updating the value of the count variable the original value + 1.

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

@@ -2,10 +2,6 @@ let firstName = "Creola";
 let middleName = "Katherine";
 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 = ``;
-
-// https://www.google.com/search?q=get+first+character+of+string+mdn
+let initials = firstName[0] + middleName[0] + lastName[0];
 
+console.log(initials);

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

@@ -10,14 +10,15 @@
 // (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}`);
-
-// 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 = ;
+// +1 to not include the slash in the base
+// lastSlashIndex finds position of the last / in the string
+// slice extracts part of the string from that position to the end
+const dir = filePath.slice(0, lastSlashIndex);
 
-// https://www.google.com/search?q=slice+mdn
+const dotIndex = base.lastIndexOf(".");
+const ext = base.slice(dotIndex);
+// dotIndex finds position of the last . in the base string and slice extracts after this
+console.log(`The base part of the file path is ${base}, the dir part is ${dir}, and the ext part is ${ext}`);

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

@@ -2,6 +2,11 @@ const minimum = 1;
 const maximum = 100;
 
 const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
+// num is an integer between minimum and maximum, between 1 and 100 inclusive 
+// math.random() produces a decimal between 0 (inclusive) and 1 (exclusive)
+// math.floor() rounds down to the nearest integer
+// (maximum - minimum + 1)) + minimum chooses a number between minimum and maximum and adds 1 so its inclusive of maximum
+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

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

@@ -2,3 +2,9 @@
 
 const age = 33;
 age = age + 1;
+// This will cause an error because age is a constant and cannot be reassigned
+console.log("I am " + age + " years old");
+// To fix the error, we can change const to let, which allows reassignment
+let age = 33;
+age = age + 1;
+console.log("I am " + age + " years old");  

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

@@ -1,5 +1,10 @@
 // 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}`);
+
+// The error is that cityOfBirth is used before it is declared. 
+// In JavaScript, variables declared with const or let cannot be accessed before their declaration due to the temporal dead zone. 
+// To fix the error, we need to declare and initialize cityOfBirth before using it in the console.log statement.
+

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

@@ -1,9 +1,12 @@
 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
+
+// slice is a method that works on strings, not numbers. 
+// To fix the error, we can convert cardNumber to a string using the toString() method before calling slice.

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

@@ -1,2 +1,5 @@
-const 12HourClockTime = "20:53";
-const 24hourClockTime = "08:53";
+const ClockTime12Hour = "08:53";
+const ClockTime24Hour = "20:53";
+// Variables cannot start with a number
+// Can only contain letters, numbers, underscores and $
+// Variables wre written wrong way around

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 +12,26 @@ 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 this file: lines 3, 4 and 7
+// Line 4: carPrice,replaceAll(",", "") removes all commas from string
+// Line 4: Number(...) converts string into number
+// Line 5: priceAfterOneYear.replaceAll("," "") removes all commas from string
+// Line 5: Number(...) converts string to number
+// Line 10: console.log(`The percentage change is ${percentageChange}`) prints percentage change to output
 
 // 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?
+// Line 5 is missing a comma in the replaceAll function call. This is causing a syntax error because the function expects two arguments, but only one is provided. 
 
 // c) Identify all the lines that are variable reassignment statements
+// Variable reassignment means giving an existing variable a new value.
+// Lines 4 and 5 reassign new values to carPrice and priceAfterOneYear respectively.
 
 // d) Identify all the lines that are variable declarations
+// Variable declaration means creating a new variable and assigning it a value for the first time.
+// 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?
+// It converts the string value of carPrice into a number value and removes the comma.

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

@@ -12,14 +12,29 @@ 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 variable declarations in this program on lines 1, 3, 4, 6, 7, 9.
 
 // b) How many function calls are there?
+// 1: console.log() on line 10.
 
 // c) Using documentation, explain what the expression movieLength % 60 represents
+// The remainder (%) operator returns the remainder left over when one operand (dividend) is divided by a second operand (divisor). 
+// It always takes the sign (+/-) of the dividend (the first number).
+// So the movie length in seconds is divided by 60 (the number of seconds in a minute).
+// The remainder is the number of seconds left over after all the full minutes have been accounted for.
 // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// It subtracts the remaining seconds from total movie length to get the total length in seconds that can be evenly divided by 60.
+// Then divides by 60 to convert the length from seconds to minutes.
+// So totalMinutes represents the total number of full 60-second minutes in the movie.
 
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
+// The variable result represents the total length of the movie in hours, minutes and seconds.
+// A better name for this variable could be movieDuration or movieFormattedLength.
 
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+// The code will work for all positive integer values of movieLength formatting to H:MM:SS
+// It will also work for 0, returning 0:0:0
+// It will incorrectly format negative numbers and very small number like < 60 seconds.
+// Single digit minutes and seconds will not be zero-padded to two digits e.g. String(remainingMinutes).padStart(2, "0")

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

@@ -1,21 +1,42 @@
 const penceString = "399p";
+// Declares constant variable named penceString and assigns the string 399p
+// This indicates price in pence
 
 const penceStringWithoutTrailingP = penceString.substring(
   0,
   penceString.length - 1
 );
+// Constant variable is declared to remove the trailing p in 399p to just keep the numeric part
+// penceString.length is number of characters in 399p = 4 so -1 is 3
+// substring(0, 3) returns the characters from index 0 up to index 3 exclusive, returning 399.
 
 const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+// padStart ensures that the string has at least 3 characters by adding leading zeros if necessary
+// This standardises the numeric string to simplify splitting into pounds and pence.
+// In this case, 399 already has 3 characters, so no padding is added.
+
 const pounds = paddedPenceNumberString.substring(
   0,
   paddedPenceNumberString.length - 2
 );
+// The last two characters represent pence
+// Const pounds is declared as a variable consisting of a substring of previously declared variable and a newly calculated variable
+// paddedPenceNumberString.length computes index where last two characters start, so that is after 1 character.
+// substring(0, 1) extracts the pounds part, by returning the characters from index 0 up to index 1 exclusive. 
+// This is "3" in this case.
 
-const pence = paddedPenceNumberString
-  .substring(paddedPenceNumberString.length - 2)
-  .padEnd(2, "0");
+const pence = paddedPenceNumberString 
+// New variable to ensure two-digit pence component is formatted correctly.
+  .substring(paddedPenceNumberString.length - 2) 
+  // returns substring from index to the end inclusive
+  // For 399, start index is character 1 (the first 9) so this returns 99.
+  .padEnd(2, "0"); 
+  // Ensures pence string has at least 2 characters by adding trailing zeros if needed
+  // So 5p would become 005 and this would return 05.
 
 console.log(`£${pounds}.${pence}`);
+// Template string  that joins pounds and pence parts with a decimal point and logs it
+// This displays the standard and prints it to the console. 
 
 // This program takes a string representing a price in pence
 // The program then builds up a string representing the price in pounds

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

@@ -4,13 +4,22 @@ 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?
+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`
+Object
 
 Answer the following questions:
 
 What does `console` store?
+Console is an object storing a collection of functions for logging, debugging and inspecting code.
+
 What does the syntax `console.log` or `console.assert` mean? In particular, what does the `.` mean?
+The dot is the property access operator in JavaScript 
+Console.log means : get the log property from the console object
+log is a function so can be called using parentheses
+console.assert can test for assumptions in the code, if the condition is true nothing happens but if its false it prints an error message.

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

@@ -1,5 +1,6 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// The variable str is being declared twice within the same scope, which will cause a syntax error.
 
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
@@ -8,6 +9,17 @@ function capitalise(str) {
   let str = `${str[0].toUpperCase()}${str.slice(1)}`;
   return str;
 }
+const result = capitalise('hello');
+console.log(result);
+// SyntaxError: Identifier 'str' has already been declared
 
 // =============> write your explanation here
+// // The first declaration is in the function parameter and the second one is inside the function body.
+// In JavaScript, you cannot declare the same variable name in the same scope using let or const.
+// To fix this, we can either rename the inner variable or assign the capitalised value to the parameter itself without redeclaring it.
+
 // =============> write your new code here
+function capitalise(str) {
+  str = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return str;
+}