Complete Sprint 2 interpret exercises

Author: maryam-devio

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;
@@ -12,11 +12,31 @@ 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/method calls:
+// Line 4: carPrice.replaceAll(",", "")
+// Line 4: Number(...)
+// Line 5: priceAfterOneYear.replaceAll(",", "")
+// Line 5: Number(...)
+// Line 10: console.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?
+// The error originally comes from line 5.
+// priceAfterOneYear was declared with const, but line 5 tries to assign a new value to it.
+// A variable declared with const cannot be reassigned, so JavaScript throws a TypeError.
+// To fix the error, change const to let because priceAfterOneYear needs to be reassigned.
 
 // c) Identify all the lines that are variable reassignment statements
+// Line 4: carPrice = Number(carPrice.replaceAll(",", ""));
+// Line 5: priceAfterOneYear = Number(priceAfterOneYear.replaceAll(",", ""));
 
 // d) Identify all the lines that are 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) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+// carPrice.replaceAll(",", "") removes all commas from the string,
+// changing "10,000" to "10000".
+// Number(...) then converts the string "10000" into the number 10000.
+// This allows carPrice to be used correctly in mathematical calculations.

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

@@ -1,25 +1,71 @@
 const movieLength = 8784; // length of movie in seconds
 
+// Test values tried:
+// const movieLength = 9893;
+// const movieLength = 223;
+// const movieLength = 50;
+// const movieLength = 345;
+// const movieLength = 600;
+// const movieLength = 400;
+// const movieLength = 90;
+// const movieLength = 189;
+
+function movieFormatting(num) {
+    if (num < 10) {
+        return "0" + num.toString();
+    } else {
+        return num.toString();
+    }
+}
+
 const remainingSeconds = movieLength % 60;
 const totalMinutes = (movieLength - remainingSeconds) / 60;
 
 const remainingMinutes = totalMinutes % 60;
 const totalHours = (totalMinutes - remainingMinutes) / 60;
 
-const result = `${totalHours}:${remainingMinutes}:${remainingSeconds}`;
+const result = `${movieFormatting(totalHours)}:${movieFormatting(remainingMinutes)}:${movieFormatting(remainingSeconds)}`;
 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 the original program:
+// movieLength, remainingSeconds, totalMinutes, remainingMinutes, totalHours, and result.
 
 // b) How many function calls are there?
+// There is 1 function call in the original program:
+// console.log(result).
 
 // c) Using documentation, explain what the expression movieLength % 60 represents
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
+// The % operator is the remainder operator. It returns the remainder after division.
+// Here, movieLength % 60 gives the number of seconds left over after dividing
+// the total movie length in seconds by 60.
+// For example, with movieLength = 8784, the remainder is 24,
+// so remainingSeconds is 24.
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// First, remainingSeconds is subtracted from movieLength.
+// This removes the leftover seconds and leaves a value that can be divided
+// evenly by 60. The result is then divided by 60 to convert the seconds
+// into the total number of whole minutes.
+// For movieLength = 8784, totalMinutes is 146.
 
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
+// result represents the movie duration in hours, minutes and seconds.
+// A more descriptive variable name could be movieDurationHHMMSS.
+// For movieLength = 8784, the formatted result is "02:26:24".
 
 // f) Try experimenting with different values of movieLength. Will this code work for all values of movieLength? Explain your answer
+// I tested the code with multiple values of movieLength, including:
+// 9893, 223, 50, 345, 600, 400, 90 and 189.
+
+// The original code works for the positive whole-number values I tested,
+// but it does not always format the output in HH:MM:SS format.
+// If the hours, minutes, or seconds are less than 10, for example 5 or 7,
+// they are displayed as a single digit instead of two digits.
+
+// I created the movieFormatting() function to add a leading 0 when a value
+// is less than 10. Otherwise, the function returns the value as a string.
+// I then tested the updated code with multiple movieLength values and
+// the tested values produced the expected HH:MM:SS formatted output.

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

@@ -1,27 +1,74 @@
 const penceString = "399p";
-
 const penceStringWithoutTrailingP = penceString.substring(
   0,
   penceString.length - 1
 );
-
 const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
 const pounds = paddedPenceNumberString.substring(
   0,
   paddedPenceNumberString.length - 2
 );
-
 const pence = paddedPenceNumberString
   .substring(paddedPenceNumberString.length - 2)
   .padEnd(2, "0");
-
 console.log(`£${pounds}.${pence}`);
+// This program takes a string representing a price in pence.
+// The program then builds up a string representing the price in pounds.
+
+// Step-by-step breakdown:
+
+// 1. const penceString = "399p";
+// Initialises the penceString variable with the string "399p".
+// This represents a price of 399 pence.
+
+// 2. penceString.length - 1
+// penceString has a length of 4. Subtracting 1 gives 3.
+// This is used to identify the position before the final "p".
+
+// 3. penceString.substring(0, penceString.length - 1)
+// substring() extracts the characters from index 0 up to, but not including,
+// index 3. This removes the trailing "p" and produces the string "399".
+
+// 4. const penceStringWithoutTrailingP = ...
+// Stores the result "399", so the price now contains only the numeric characters.
+
+// 5. penceStringWithoutTrailingP.padStart(3, "0")
+// padStart() makes sure the string contains at least 3 characters.
+// If it has fewer than 3 characters, "0" is added to the beginning.
+// For "399", no padding is needed, so the value remains "399".
+// This is useful for smaller values such as "99", which would become "099".
+
+// 6. const paddedPenceNumberString = ...
+// Stores the padded string. For the current input, its value is "399".
+
+// 7. paddedPenceNumberString.length - 2
+// This calculates the position that separates the pounds from the final
+// two digits representing pence. For "399", the length is 3, so 3 - 2 = 1.
+
+// 8. paddedPenceNumberString.substring(
+//      0,
+//      paddedPenceNumberString.length - 2
+//    )
+// Extracts the characters before the final two digits.
+// For "399", this extracts "3", which represents the pounds.
+
+// 9. const pounds = ...
+// Stores the pounds part of the price. In this example, pounds is "3".
+
+// 10. paddedPenceNumberString
+//       .substring(paddedPenceNumberString.length - 2)
+// substring() starts two characters from the end of the string.
+// For "399", it extracts "99", which represents the pence part.
 
-// This program takes a string representing a price in pence
-// The program then builds up a string representing the price in pounds
+// 11. .padEnd(2, "0")
+// Makes sure the pence part contains at least two characters.
+// If necessary, "0" is added to the end until the string has a length of 2.
+// In this example, "99" already has two characters, so it remains "99".
 
-// You need to do a step-by-step breakdown of each line in this program
-// Try and describe the purpose / rationale behind each step
+// 12. const pence = ...
+// Stores the final pence part. In this example, pence is "99".
 
-// To begin, we can start with
-// 1. const penceString = "399p": initialises a string variable with the value "399p"
+// 13. console.log(`£${pounds}.${pence}`);
+// Uses a template literal to combine the pound sign, pounds value,
+// decimal point and pence value.
+// With the input "399p", the final output is "£3.99".