3-to-pounds.js

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

// You need to do a step-by-step breakdown of each line in this program
// Try and describe the purpose / rationale behind each step

// 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): creates 
// a new string variable that contains the original string without the last character (the "p"). 
// 3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0"): creates a new 
// string variable that pads the previous string with leading zeros until it is at least 3 characters 
// long. eg. "45" becomes "045" and "7" becomes "007".
// 4. const pounds = paddedPenceNumberString.substring(0, paddedPenceNumberString.length - 2): creates 
// a new string variable that contains the first part of the padded string, which represents the pounds.
// It takes all characters except the last two. eg. "045" becomes "0" and "399" becomes "3".
// 5. const pence = paddedPenceNumberString.substring(paddedPenceNumberString.length - 2).padEnd(2, "0"): 
// creates a new string variable that contains the last two characters of the padded string, which represents 
// the pence. It also pads it with trailing zeros if necessary to ensure it is 2 characters long. eg. "045" 
// becomes "45" and "7" becomes "70".
// 6. console.log(`£${pounds}.${pence}`): outputs the final price in pounds and pence format to the console. 
// For example, if penceString is "399p", it will output "£3.99". If penceString is "45p", it will output "£0.45". 
// If penceString is "7p", it will output "£0.07".