London | 26-ITP-May | Martin Mwaka | Sprint 1 | Coursework Exercises

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
+
+// Martin answer - line 3 is updating the value of count by one and saving the new value back to the count variable.  The value of count will now be 1.

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 = `${firstName.slice(0, 1)}${middleName.slice(0, 1)}${lastName.slice(0, 1)}`;
+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);
+console.log(dir);
+const ext = filePath.slice(filePath.lastIndexOf("."));
+console.log(ext);
 
-// https://www.google.com/search?q=slice+mdn
+// https://www.google.com/search?q=slice+mdn

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

@@ -7,3 +7,5 @@ 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
+
+// Martin answer - num is a random integer between minimum and maximum. Math.random() generates a decimal between 0 (inclusive) and 1 (exclusive). Multiplying it by (maximum - minimum + 1) scales it to the size of the range. Math.floor() rounds it down to the nearest whole number, and adding minimum shifts the range so the lowest possible number is minimum (1) and the highest possible number is maximum (100).

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

@@ -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;
+
+// Martin comment - const cannot be reassigned.  I have changed the declaration to let which allows the value of age to be reassigned

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

@@ -1,5 +1,7 @@
 // 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}`);
+// Martin response - cityOfBirth was being logged before it was declared.  I have moved the variable initialisation above the console.log line and this now works as expected.
+
 const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);

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

@@ -1,9 +1,14 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
+const last4Digits = cardNumber % 10000;
+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
+
+// Martin comment before running the code - Slice is a string method.  In this case it fails because it is being used against a number
+
+// Martin comment after running the code - when I run the code it gives the error - 'number.slice is not a function'.  When I research online I discover this error occurs when the slice method is applied to a value that is not a string or an array.  I have resolved this by doing research on line and discovering that modulo can be used to extract digits from a long number

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

@@ -1,2 +1,6 @@
-const 12HourClockTime = "8:53pm";
-const 24hourClockTime = "20:53";
+const _12HourClockTime = "8:53pm";
+console.log(_12HourClockTime);
+const _24hourClockTime = "20:53";
+console.log(_24hourClockTime);
+
+// Martin comment - a variable cannot begin with a number.  I have converted both to start with an underscore

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 +13,19 @@ 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
 
+// Martin answer - functions calls are on lines - 4, 5 with the use of the Number function
+
 // 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?
 
+// Martin answer - There is a syntax error on line 5, comma missing between current item and replacement item in replaceAll method
+
 // c) Identify all the lines that are variable reassignment statements
 
+// Martin answer - lines 4 and 5
+
 // d) Identify all the lines that are variable declarations
+// Martin answer - lines 1, 2, 7 and 8
 
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+
+// Martin answer - the purpose of this expression is to use the replace all method to replace the comma in the carPrice price expression with a blank so that the expression reads "10000".  This is converted to a number using the number function converting the string "10000" to a number 10000

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

@@ -13,13 +13,30 @@ console.log(result);
 
 // a) How many variable declarations are there in this program?
 
+// Martin answer - there are 6 variable declarations on lines 1, 3, 4, 6, 7, 9
+
 // b) How many function calls are there?
 
+// Martin answer - there are no function calls
+
 // c) Using documentation, explain what the expression movieLength % 60 represents
 // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
 
+// Martin answer - the expression movieLength % 60 uses the modulo operator which extracts the value remaining seconds after movieLength is divided by 60
+
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
 
+// Martin answer - the expression totalMinutes = (movieLength - remainingSeconds) / 60 subtracts remaining seconds from movieLength (total length of movie in seconds) and divides the result by 60 (representing seconds in one minute) to return the total number of minutes
+
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
 
+// Martin answer - result represents a formatted express of the movie duration as hours, minutes and seconds.  A better name for this variable is formattedMovieDuration
+
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+
+/* - Martin answer - it works for numerical numbers I have tried, positive and negative, but in the real world you would want to prevent entry of negative numbers.  
+I have tried adding trailing zeros (8784.00), but JavaScript automatically converts them to a number - 8784.  
+I have tried converting it to a string ("8784" or "8784.00"), but I get the same results as JavaScript automatically converts them to a number.
+Enter text returns all values as NaN - NaN:NaN:NaN
+
+*/

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

@@ -6,6 +6,7 @@ const penceStringWithoutTrailingP = penceString.substring(
 );
 
 const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+
 const pounds = paddedPenceNumberString.substring(
   0,
   paddedPenceNumberString.length - 2
@@ -25,3 +26,17 @@ console.log(`£${pounds}.${pence}`);
 
 // To begin, we can start with
 // 1. const penceString = "399p": initialises a string variable with the value "399p"
+
+// MARTIN ANSWERS BELOW
+/*
+ 1. const penceString = "399p" - initialises a string variable with the value of "399p"
+ 2. const penceStringWithoutTrailingP = penceString.substring(0,penceString.length - 1) - removes the trailing p so that the value of penceStringWithoutTrailingP is "399"
+ 3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0") pads the value to a minimum of 3 spaces, with 0 being added if the value is less than 3 characters. In this case holding there are 3 characters - "399". 
+ 4. const pounds = paddedPenceNumberString.substring(0,paddedPenceNumberString.length - 2); - uses the substring method to extract the first value from paddedPenceNumberString and assign it to the variable pounds.  In this case the first value is "3"
+ 5. const pence = paddedPenceNumberString
+  .substring(paddedPenceNumberString.length - 2)
+  .padEnd(2, "0");
+  - this uses the substring method to extract the last 2 values in paddedPenceNumberString, followed immediately with the padEnd method which adds zeros if the number of characters is less than 2 spaces.  In this case, the value of "99" is assigned to the pence variable
+
+ 6. console.log(`£${pounds}.${pence}`) is a log of the variables pounds and pence in a formatted string which will print the value - "£3.99"
+*/