LONDON-JAN-25 | ANDREI FILIPPOV | Module-Structuring-and-Testing-Data | WEEK 1

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
+
+// line 3 adds 1 to count and then saves this change to count variable

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

@@ -5,7 +5,8 @@ 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 = ``;
-
-// https://www.google.com/search?q=get+first+character+of+string+mdn
+let initials = `${firstName.charAt(0)}${middleName.charAt(0)}${lastName.charAt(
+  0
+)}`;
 
+console.log(initials);

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

@@ -9,15 +9,18 @@
 
 // (All spaces in the "" line should be ignored. They are purely for formatting.)
 
-const filePath = "/Users/mitch/cyf/Module-JS1/week-1/interpret/file.txt";
+const filePath = "/Users/mitch/cyf.old/folder.bak/file.txt";
 const lastSlashIndex = filePath.lastIndexOf("/");
 const base = filePath.slice(lastSlashIndex + 1);
 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);
+const ext = filePath.slice(filePath.lastIndexOf(".") + 1);
 
-// https://www.google.com/search?q=slice+mdn
+console.log(dir);
+console.log(ext);
+
+// https://www.google.com/search?q=slice+mdn

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

@@ -3,7 +3,17 @@ 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
+
+/* 
+In 1 step program calculates "(maximum - minimum + 1)", which evaluates to 100. This is the total range of numbers between 1 and 100
+In 2 step program multiples 100 by floating point, random number, that's greater than or equal to 0 and less than 1
+In 3 step program the Math.floor function rounds the result down to the nearest whole number
+In 4 step program adds 1 to the number returned by Math floor function
+
+I would say, that num function represent a random amount of percents
+*/

Sprint-1/2-mandatory-errors/0.js

@@ -1,2 +1,6 @@
+/*
 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?
+We don't want the computer to run these 2 lines - how can we solve this problem?
+*/
+
+//we can use "/* */" for this task

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;
+
+//  A constant cannot change value through assignment, so we need to change const to let in order to change the value

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

@@ -1,5 +1,10 @@
 // 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}`);
+
+/*
+program couldn't find variable, because it was declared after calling, which is not correct
+problem was solved by moving variable declaration above the calling
+*/

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

@@ -1,9 +1,18 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
-
+const last4Digits = String(cardNumber).slice(-4);
+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
+
+/*
+I predict that the code isn't working because the slice function can only extract the text from string but cardNumber is stored as an integer number.
+
+After running the code, I got "TypeError", which confirms that slice is incompatible with the data type stored in cardNumber.
+This is exactly what I predicted.
+
+After converting cardNumber to a string using "String()", I've got the correct value 
+*/

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

@@ -1,2 +1,6 @@
-const 12HourClockTime = "20:53";
-const 24hourClockTime = "08:53";
+const hourClockTime24 = "20:53";
+const hourClockTime12 = "08:53";
+
+/*
+Syntax Error. Variable names must begin with a letter, so '12HourClockTime' is not valid name.
+*/

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;
@@ -12,11 +12,25 @@ 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
+// 5
+// carPrice = Number(carPrice.replaceAll(",", ""));
+// priceAfterOneYear = Number(priceAfterOneYear.replaceAll("," ""));
+// console.log(`The percentage change is ${percentageChange}`);
 
 // 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?
+// error occurring in line "priceAfterOneYear = Number(priceAfterOneYear.replaceAll("," ""));"
+// the error occurred because js didn't understand where argument list ends
+// we just need to place a comma between items in list
 
 // c) Identify all the lines that are variable reassignment statements
+// carPrice = Number(carPrice.replaceAll(",", ""));
+// priceAfterOneYear = Number(priceAfterOneYear.replaceAll(",",""));
 
 // d) Identify all the lines that are variable declarations
+// let carPrice = "10,000";
+// let priceAfterOneYear = "8,543";
+// const priceDifference = carPrice - priceAfterOneYear;
+// const percentageChange = (priceDifference / carPrice) * 100;
 
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+// the purpose of this expression is to convert string data type to integer data type

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

@@ -1,4 +1,4 @@
-const movieLength = 8784; // length of movie in seconds
+const movieLength = 1000000.52; // length of movie in seconds
 
 const remainingSeconds = movieLength % 60;
 const totalMinutes = (movieLength - remainingSeconds) / 60;
@@ -12,14 +12,21 @@ 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?
+// 6
 
 // b) How many function calls are there?
+// 1
 
 // c) Using documentation, explain what the expression movieLength % 60 represents
 // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
+// it represent the remainder left over after one operand is divided by a second operand.
 
 // d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+// this means an integer number of minutes
 
 // e) What do you think the variable result represents? Can you think of a better name for this variable?
+// variable represents a string in the format 'HH:MM:SS'
+// I think 'totalLength' would be 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
+// This code will only work for Number data type

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

@@ -1,4 +1,4 @@
-const penceString = "399p";
+const penceString = "099p";
 
 const penceStringWithoutTrailingP = penceString.substring(
   0,
@@ -13,7 +13,6 @@ const pounds = paddedPenceNumberString.substring(
 
 const pence = paddedPenceNumberString
   .substring(paddedPenceNumberString.length - 2)
-  .padEnd(2, "0");
 
 console.log(`£${pounds}.${pence}`);
 
@@ -23,5 +22,24 @@ console.log(`£${pounds}.${pence}`);
 // 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"
+/*
+To begin, we can start with
+1. const penceString = "399p": initialises a string variable with the value "399p"
+2.
+3. const penceStringWithoutTrailingP = penceString.substring( : declares a variable equals to 'penceString', but without p at the end
+4. substring starts from first character
+5. ends on the last character before 'p'
+6.
+7.
+8. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0"); : pads the string with "0" until the total length of string reaches the length 3
+9. const pounds = paddedPenceNumberString.substring( : declares a variable 'pounds' equals to 'paddedPenceNumberString' but without last two digits
+10. substring starts from first character
+11. ends on the third character from the end.
+12.
+13.
+14. const pence = paddedPenceNumberString:  declares a variable 'pence' equals to last two digits of 'paddedPenceNumberString'
+15. returns the part of the 'paddedPenceNumberString' string from the second digit up to the end
+16. pads the string with "0" in the end until the total length of string reaches the length 2
+17.
+18. writes in the console price in pounds
+*/