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 the variable count by one and reassigning it back to the variable. This can also be written in shorthand using an increment operator - count++

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 = `${firstName[0]}${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);
+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 +7,9 @@ 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 (0,1), which is rounded down to the nearest integer by the Math.floor method.  After multiplication the range is scaled up. Math.random is generating a random number up to 100 - 
+Math.floor(Math.random() * (maximum - minimum + 1)  →  [0, 100))
+Adding minimum  - Math.floor(Math.random() * (maximum - minimum + 1)) + minimum - shifts the range up by 1 and the maximum number is now included in the range [mimimum, maximum] eg [1, 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).toString().padStart(4, "0");
+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. By converting it to a string and adding a padStart of 4 characters, I ensure that 4 string characters are returned even in the event of a number such as 12340000

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 +13,21 @@ 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 replaceAll method using a search string and replacement string. In this case all commas are removed from carPrice (",") and replaced with a blank (""), converting the formatted number of "10,000" to "10000". This is passed into a Number() method which converts the string 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"
+*/