Manchester | 26-ITP-Sep | Precious Moses | Sprint 2 | Course-work-2

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

@@ -4,3 +4,9 @@ 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
+console.log(count);
+
+//Line 3 reads the current value of <count>, which is <0>, and computes <count + 1>, which turns out to be 1.
+//It also assigns the new value <1> to the variable <count>, overwriting the initial value <0>.
+//The assignment operator "=" means, take the value on the right, and store it in the variable on the left.
+//Console.log(count) prints out the result of Line 3.

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

@@ -5,6 +5,7 @@ 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 = ``;
+//Solution
+const initials = `${firstName[0]}${middleName[0]}${lastName[0]}`;
 
-// https://www.google.com/search?q=get+first+character+of+string+mdn
+// console.log(initials);

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

@@ -17,7 +17,12 @@ 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 = ;
+//Solution
+const dir = filePath.slice(0, lastSlashIndex);
+console.log(`The dir part of ${filePath} is ${dir}`);
+
+const lastDotIndex = base.lastIndexOf(".");
+const ext = base.slice(lastDotIndex);
+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

@@ -2,8 +2,24 @@ const minimum = 1;
 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
+
+//Solution
+//- "num" represents a random whole number between 1 and 100.
+
+//Break down of expression
+//-Math.random: This generates a random decimal number between 0 and 1. It can return 0, but never reaches 1. (Example: 0.876).
+
+//-(maximum - minimum + 1): 
+// This expression can be simplified as (100 - 1 + 1), which equals 100. This tells the program how many possible whole numbers there are. There are 100 possibilities.
+// The +1 is important as without it, we would only reach 99 possibilities, that is 0 - 99.
+
+//-Math.random() * (maximum - minimum + 1):
+// This function multiplies the random decimal by the range size. Since Math.random() represents numbers >=0 and <1, this expression produces value anywhere from 0 up to 100, excluding 100.
+// Example to justify expression: 0.876 * 100 = 87.6 
+
+//-Math.floor: This static method rounds down to the nearest whole number, discarding the decimal. This turns the continuous range into whole numbers, from 0 - 99.
+// That is 87.6 becomes 87.
+
+// + minimum: This shifts the whole range up by adding 1. So instead of landing on 0 - 99, we have 1 - 100.

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

@@ -1,2 +1,5 @@
-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?*/
+
+//Solution
+//This problem was solved by wrapping the statement in a multi-line comment tag. This way the lines are stopped from executing.

Sprint-2/2-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;
+
+console.log(age);

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}`);
+
+
+//ReferenceError: Cannot access 'cityOfBirth' before initialization.
+//console.log tries to use cityOfBirth inside the template literal, but cityOfBirth has not been declared yet at that point in the code.

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

@@ -1,9 +1,21 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
+const last4Digits = String(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
+
+
+//Solution 
+//Prediction - The code would not run because 'cardNumber' is declared as numbers instead of a string.
+//             The '.slice()' method belongs to strings and arrays, it could only work by treating it's subject as a sequence of characters.
+
+console.log(last4Digits);
+
+//Error message - TypeError: cardNumber.slice is not a function
+//Reason for error
+//The error thrown was considerably as predicted.
+//'.slice()' is a method defined on 'String.prototype', and since 'cardNumber' was declared with a numeric literal, JavaScript treats it as the 'number' type.

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

@@ -1,2 +1,7 @@
-const 12HourClockTime = "8:53pm";
-const 24hourClockTime = "20:53";
+const ClockTime12Hour = "8:53pm";
+const ClockTime24hour = "20:53";
+
+console.log(ClockTime12Hour, ClockTime24hour);
+
+//There is a SyntaxError after running the code.
+//This error occurred because the identifiers '12HourClockTime' and '24hourClockTime' both start with a digit.

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;
@@ -20,3 +20,33 @@ console.log(`The percentage change is ${percentageChange}`);
 // d) Identify all the lines that are variable declarations
 
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+
+
+//Solution
+// a) There are 5 function calls on lines 4, 5, and 9.
+//    Line 4: carPrice.replaceAll(",","")
+//    Line 4: Number()
+//    Line 5: priceAfterOneYear.replaceAll("," "")
+//    Line 5: Number()
+//    Line 10: console.log()
+
+// b) Line 5 seems to broken.
+// Error message - SyntaxError: missing ) after argument list
+// Reason for error: There is a missing comma between two arguments of replaceAll.
+// To fix the error, we need to add the missing comma between the arguments of replaceAll.
+
+// c) Lines 4 and 5 contain variable reassignment statements
+//    Line 4: carPrice = Number()
+//    Line 5: priceAfterOneYear = Number()
+
+// d) Lines 1, 2, 7, and 8 contain variable declarations
+//    Line 1: let carPrice = "10,000";
+//    Line 2: let priceAfterOneYear = "8,543";
+//    Line 7: const priceDifference = carPrice - priceAfterOneYear;
+//    Line 8: const percentageChange = (priceDifference / carPrice) * 100;
+
+// e) Number(carPrice.replaceAll(",","")) is two steps combined, whereby:
+//    carPrice.replaceAll(",","") takes the string "10,000" and deletes every comma, making it 10000
+//    and Number() converts the new string into an actual numeric value
+// The purpose of the expression is to strip out the formatting comma first from the string
+// so that JavaScript does not treat it as plain text, and then converts the result into real numbers for it to be used in math, similar to Line 7  

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

@@ -1,13 +1,20 @@
-const movieLength = 8784; // length of movie in seconds
+//const movieLength = 8784; // length of movie in seconds
+function convert(movieLength){
 
 const remainingSeconds = movieLength % 60;
 const totalMinutes = (movieLength - remainingSeconds) / 60;
 
 const remainingMinutes = totalMinutes % 60;
 const totalHours = (totalMinutes - remainingMinutes) / 60;
 
-const result = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
-console.log(result);
+return `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
+//const result = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
+//console.log(result);
+}
+
+[65, -100, 90.5, "8784"].forEach(v => {
+    console.log(v, "->", convert(v));
+});
 
 // For the piece of code above, read the code and then answer the following questions
 
@@ -23,3 +30,35 @@ console.log(result);
 // 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
+
+
+
+//Solution
+// a) There are 6 declared variables in this program, all declared with 'const'
+//   - const movieLength
+//   - const remainingSeconds
+//   - const totalMinutes
+//   - const remainingMinutes
+//   - const totalHours
+//   - const result
+
+// b) There is just 1 function call: console.log(result);
+
+// c) In the expression 'movieLength % 60', '%' represents the remainder operator. It returns the value that of what is left over after dividing the left operand by the right operand as many whole times as possible.
+//    Since movieLength = 8784, it means: 8784 % 60, which returns a result of 146 remainder 24.
+//    Therefore, movieLength % 60 (8784 % 60) returns the leftover value '24'. In this context, the leftover represents the loose seconds that add up to a full minute.
+
+// d) The expression assigned to totalMinutes simply means, we subtract the loose seconds, '24', from movieLength, '8784'. The result becomes a number easily divisible by 60
+//    That is: totalMinutes = (8784 - 24); 
+//              which gives 8760, and then divides it 60;
+//              the result, 146, is the total number of complete minutes contained in the movie
+
+// e) The variable 'result' is a template literal syntax which holds the movie's length formatted as a colon-separated time string: as in '2:26:24'.
+//    A better name for 'result' could have been 'movieLengthDisplay'
+
+// f) This program did not work for all values of movieLength
+//  Some problems discovered
+// - for movieLength 65 there was an issue with zero-padding, '65' becomes '0:1:5' instead of the conventional '00:01:05'. Returning single-digit minutes/seconds look wrong in a real time display
+// - negative integer, '-100', produced '0:-1:-40', which is inaccurate for a duration
+// - non-integer input, 90.5, was not handled as it gives '0:1:30.5'. This implies that a fractional second had slipped through untouched, since nothing was truncated.
+// - string input "8784" works here because operators '%', '-', and '/' automatically converts strings to numbers, but that is fragile and relies on the type conversion rather than actual input validation 

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

@@ -25,3 +25,30 @@ 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);
+//    substring(0, length - 1): is a method that is invoked in the paragraph above to take every character in the string provided except the last one, leaving out the 'p'
+//    That is -> '399p' becomes '399'
+//    const penceStringWithoutTrailingP: used to store the value from 'penceString.substring(...)'
+
+// 3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+//    penceStringWithoutTrailingP is now '399'
+//    padStart(3, "0") is a method used above which guarantees that the numeric string is at least 3 characters long, and if it is shorter add '0' to the front until it is 3 characters long.
+//    padding to 3 ensures there is always at least 3 digits, that is, one pounds digit and two pence digits. 
+//    
+
+// 4. const pounds = paddedPenceNumberString.substring(0, paddedPenceNumberString.length - 2);
+//    since paddedPenceNumberString is '399' and it's '.length' is 3
+//    this line is saying: '399.substring(0, 3 - 2)', which becomes '399.substring(0, 1)'
+//    'substring' is a method used to grab characters from this string, starting from the left, from position '0' up to, but not including, position '1'
+//    'const pounds' would be assigned the new value: '3'
+
+// 5. const pence = paddedPenceNumberString.substring(paddedPenceNumberString.length - 2).padEnd(2, "0");
+//    since paddedPenceNumberString.length is '3'
+//    then 'paddedPenceNumberString.substring(3 - 2)' becomes 'paddedPenceNumberString.substring(1)': this means grab everything from position '1' of the string to the end.
+//    That is -> '399.substring(1)' becomes '99' 
+//    '.padEnd(2, "0") is another method that ensures the string is at least 2 characters long and adding '0' to the end if it's too short.
+//    'const pence' would be assigned the new value: '99'
+
+// 6. console.log(`£${pounds}.${pence}`): This template string calls the result of two pieces, 'pounds' which is '3' and 'pence' which '99'
+//    Overall result: £3.99