Pull in solutions branch from Module-Structuring-And-Testing-Data

Author: illicitonion

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

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+let count = 0;
+
+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
+
+// =============> assign the value of count + 1 to count
+// =============> count held the value 0, so count + 1 = 1
+// =============> the value of count is now 1
+
+console.assert(count === 1);

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

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+let firstName = "Creola";
+let middleName = "Katherine";
+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 = `${firstName[0]}${middleName[0]}${lastName[0]}`;
+
+console.assert(initials === "CKJ");
+
+// https://www.google.com/search?q=get+first+character+of+string+mdn

Sprint-2/1-key-exercises/3-paths.js

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+// The diagram below shows the different names for parts of a file path on a Unix operating system
+
+// ┌─────────────────────┬────────────┐
+// │          dir        │    base    │
+// ├──────┬              ├──────┬─────┤
+// │ root │              │ name │ ext │
+// "  /    home/user/dir / file  .txt "
+// └──────┴──────────────┴──────┴─────┘
+
+// (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 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 = filePath.slice(0, lastSlashIndex);
+const ext = base.slice(base.lastIndexOf("."));
+
+console.assert(dir === "/Users/mitch/cyf/Module-JS1/week-1/interpret");
+console.assert(ext === ".txt");
+
+// https://www.google.com/search?q=slice+mdn

Sprint-2/1-key-exercises/4-random.js

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+const minimum = 1;
+const maximum = 100;
+
+const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
+
+// 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
+
+console.log(num);
+
+// following the order of operations, the expression inside the Math.floor() function is evaluated first
+// Math.random() generates a random number between 0 and 1
+// multiplying this by (maximum - minimum + 1) will give a number between 0 and 100
+// moving out of the parentheses, the Math.floor() function rounds this number down to the nearest whole number
+// adding the minimum value of 1 to this will give a number between 1 and 100
+
+console.assert(num >= 1 && num <= 100);
+console.assert(Number.isInteger(num));
+
+// =========================>  Question for reviewer
+// I think I understand what it does
+// But I'd like to know when I might use the Math.random() function?

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

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

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+// trying to create an age variable and then reassign the value by 1
+
+let age = 33;
+age = age + 1;
+
+// =============> TypeError: Assignment to constant variable.
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_const_assignment
+// =============> I fixed the error by changing the const keyword to let, which allows the value to be reassigned

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

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+// Currently trying to print the string "I was born in Bolton" but it isn't working...
+// what's the error ?
+
+const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);
+
+// =============> ReferenceError: Cannot access 'cityOfBirth' before initialization
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Cant_access_lexical_declaration_before_init
+// =============> I fixed the error by moving the console.log() statement below the declaration of the cityOfBirth variable

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

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+const cardNumber = 4533787178994213;
+
+// 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
+
+// =============> My prediction
+// I think the code will throw an error because the cardNumber variable is a Number and not a String data type
+// The slice() method is a String method and cannot be used on a Number
+// https://www.w3schools.com/js/js_datatypes.asp
+// I predict that the error will be a TypeError
+
+// =============> The actual output
+// TypeError: cardNumber.slice is not a function
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_function
+
+// =============> My explanation
+// The error is as I predicted. I need to convert the cardNumber variable to a string before using the slice() method
+// And then convert the last4Digits variable back to a number
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/Number
+
+const last4DigitsString = cardNumber.toString().slice(-4);
+const last4DigitsNumber = Number(last4DigitsString);
+
+console.assert(last4DigitsNumber === 4213);

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

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+// const 12HourClockTime = "20:53";
+// const 24hourClockTime = "08:53";
+
+const clockTime12 = "20:53";
+const clockTime24 = "08:53";
+
+// ===========> Prediction
+// 12HourClockTime is not a valid variable name because it starts with a number.
+// If I try to run the code, I will get a SyntaxError
+
+// ===========> Execution
+// SyntaxError: Invalid or unexpected token
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Identifier_after_number
+
+// ===========> Solution
+// I needed to change the variable name to something that starts with a letter
+// Variables must begin with a letter, $, or _ . The first character cannot be a number.

Sprint-2/3-mandatory-interpret/1-percentage-change.js

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+let carPrice = "10,000";
+let priceAfterOneYear = "8,543";
+
+carPrice = Number(carPrice.replaceAll(",", ""));
+priceAfterOneYear = Number(priceAfterOneYear.replaceAll(",", ""));
+
+const priceDifference = carPrice - priceAfterOneYear;
+const percentageChange = (priceDifference / carPrice) * 100;
+
+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
+// Line 4 calls the replaceAll() function and the Number() function
+// Line 5 calls the replaceAll() function and the Number() function
+// Line 10 calls the console.log() 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?
+// priceAfterOneYear = Number(priceAfterOneYear.replaceAll("," ""));
+//                                                      ^^^
+
+// SyntaxError: missing ) after argument list
+// The error is occurring because there is a missing comma in the replaceAll() function
+// The replaceAll() function should be replaceAll(",", "") like the one on line 4
+// I've fixed it by adding the comma
+
+// c) Identify all the lines that are variable reassignment statements
+// Line 4 and Line 5 are variable reassignment statements. The variables carPrice and priceAfterOneYear are being reassigned to new values
+
+// d) Identify all the lines that are variable declarations
+// 1,2,7,8 are variable declarations. The variables carPrice, priceAfterOneYear, priceDifference, and percentageChange are being declared
+
+// e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+
+// working from the inside out:
+// the replaceAll() function is removing the comma from the string stored in the carPrice variable
+// the Number() function is converting the string to a number