Brussels | 25-ITP-October | Serotonine | Sprint 2 | All exercices

.gitignore

@@ -1,4 +1,5 @@
 node_modules
 .DS_Store
 .vscode
-**/.DS_Store
+**/.DS_Store
+package-lock.json

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

@@ -1,6 +1,12 @@
 let count = 0;
-
+/* Incrementing by 1 the count value. */
+count = count + 1;
+/* Check if count === 1. */
+console.log(count);
+/* Incrementing by 1 the count value. */
 count = count + 1;
+/* Check if count === 2. */
+console.log(count);
 
 // 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

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

@@ -4,8 +4,10 @@ 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 = ``;
+/* So many ways to get the first char of a string ! */
+let initials = `${firstName.charAt(0)}${middleName[0]}${lastName.slice(0, 1)}`;
+/* Check if ok */
+console.log(initials);
 
 // https://www.google.com/search?q=get+first+character+of+string+mdn
 

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

@@ -14,10 +14,15 @@ 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
+// Create a variable to store the directories part of the filePath variable.
+// Create a variable to store the extension part of the variable.
 
-const dir = ;
-const ext = ;
+/* Funny ! */
+const dir = filePath.slice(0, lastSlashIndex + 1);
+const lastPointIndex = filePath.lastIndexOf(".");
+const ext = filePath.slice(lastPointIndex + 1);
+/* Check */
+console.log("The directories part of the filePath is : " + dir);
+console.log("The extension part of the variable is : " + 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

@@ -1,7 +1,37 @@
 const minimum = 1;
 const maximum = 100;
 
+/*
+ * Well-known JavaScript pattern for generating random integers
+ * in a specific range [minimum, maximum] (both inclusive).
+ * minimum <= num <= maximum.
+ */
+/* Shift along the range from min to max. */
 const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
+/* Check */
+let counter = 0;
+const min = 5;
+const max = 20;
+
+while (counter <= 5) {
+  console.log("\nMinimum", min, "Maximum", max);
+  // Mystery of Mathematics.
+  const m = max - min + 1;
+  console.log("(max - min + 1) => ", m);
+  /*  return random float in between 0 and 1 (non inclusive) */
+  const rd = Math.random();
+  console.log("random", rd);
+  // Mystery of Mathematics.
+  console.log(`(${m} * random) => `, m * rd);
+  /* Math.floor return the nearest lower integer
+   * E.g.  Math.floor(3.9) === 3;
+   * Return a range 0 => 99.
+   */
+  const int = Math.floor(rd * m);
+  console.log(`Math.floor(${m} * random) =>`, int);
+  console.log(`${int} + ${min} =>`, Math.floor(rd * m) + min);
+  counter++;
+}
 
 // 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

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

@@ -1,2 +1,5 @@
-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? */
+/*
+ * Just comment it.
+*/

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

@@ -1,4 +1,7 @@
 // trying to create an age variable and then reassign the value by 1
-
-const age = 33;
+/* TypeError: Assignment to constant variable. */
+// const age = 33;
+let age = 33;
 age = age + 1;
+/* Check if ok. */
+console.log(age);

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}`);
 const cityOfBirth = "Bolton";
+console.log(`I was born in ${cityOfBirth}`);
+/* Cannot access 'cityOfBirth' before initialization */
+// const cityOfBirth = "Bolton";

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

@@ -1,5 +1,16 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
+/* cardNumber is a number but slice() is a String method. */
+/* TypeError: cardNumber.slice is not a function. */
+//const last4Digits = cardNumber.slice(-4);
+const last4Digits = cardNumber.toString().slice(-4);
+/* Another way to cast a number (string + number == string) */
+const otherLast4Digits = `${cardNumber}`.toString().slice(-4);
+const anotherLast4Digits = ("" + cardNumber).slice(-4);
+/* Check if ok */
+console.log(last4Digits);
+console.log(otherLast4Digits);
+console.log(anotherLast4Digits);
+
 
 // The last4Digits variable should store the last 4 digits of cardNumber
 // However, the code isn't working

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

@@ -1,2 +1,9 @@
-const 12HourClockTime = "20:53";
-const 24hourClockTime = "08:53";
+/* Js variables are not allowed to start with digit */
+/* SyntaxError: Invalid or unexpected token */
+// const 12HourClockTime = "20:53";
+// const 24hourClockTime = "08:53";
+const hourClockTime12 = "20:53";
+const hourClockTime24 = "08:53";
+/* Check if ok. */
+console.log("hourClockTime12 : " +  hourClockTime12);
+console.log("hourClockTime24 : " +  hourClockTime24);

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

@@ -2,21 +2,42 @@ 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;
 
-console.log(`The percentage change is ${percentageChange}`);
+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
+// a) How many function calls are there in this file? 
+// Write down all the lines where a function call is made.
+/*
+ * line 4 & 5 => replaceAll() - String method.
+ * line 4 & 5 => Number() - built-in constructor function
+ * line 10 => console.log() - built-in constructor 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?
+// 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?
+/*
+ * line 5 => Miss a comma in arguments declaration.
+*/
 
 // c) Identify all the lines that are variable reassignment statements
+/*
+ * lines 4 & 5 => carPrice & priceAfterOneYear are reassigned.
+*/
 
 // d) Identify all the lines that are variable declarations
-
-// e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+/*
+ * lines 1 & 2 => carPrice & priceAfterOneYear.
+ * lines 7 & 8 => priceDifference & percentageChange.
+*/
+
+// e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing
+//  what is the purpose of this expression?
+/*
+ * Cast a string to Number.
+*/

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

@@ -1,4 +1,4 @@
-const movieLength = 8784; // length of movie in seconds
+const movieLength = -8784; // length of movie in seconds
 
 const remainingSeconds = movieLength % 60;
 const totalMinutes = (movieLength - remainingSeconds) / 60;
@@ -12,14 +12,40 @@ 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 variable's declarations:
+ * movieLength, remainingSeconds, totalMinutes, remainingMinutes, totalHours, result.
+*/
 
 // b) How many function calls are there?
+/*
+ * Only console.log()
+*/
 
 // c) Using documentation, explain what the expression movieLength % 60 represents
 // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
+/*
+ * Modulo (%) is use to return the rest number of a division.
+ * 8784 % 60 = 8784 - (60 × Math.floor(8784 / 60));
+*/
+console.log( "\nModule explained");
+console.log("8784 % 60 =" ,8784 - (60 * Math.floor(8784 / 60)));
 
-// d) Interpret line 4, what does the expression assigned to totalMinutes mean?
-
-// e) What do you think the variable result represents? Can you think of 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
+// d) Interpret line 4, what does the expression assigned to totalMinutes mean?
+/*
+ * The rest number are the seconds.
+ * We substract them to the time length then timelength / 60 result 
+ * is minutes (60 seconds in a minute).
+*/
+
+// e) What do you think the variable result represents? 
+// Can you think of a better name for this variable?
+ /* getClockTime() */
+
+// f) Try experimenting with different values of movieLength. 
+// Will this code work for all values of movieLength? Explain your answer
+/*
+ * Yes but the result display is not optimal in case 
+ * movieLength = 0 ormovieLength < 0 or totalHours === 0 or some of the value < 10.
+*/

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

@@ -10,6 +10,8 @@ const pounds = paddedPenceNumberString.substring(
   0,
   paddedPenceNumberString.length - 2
 );
+console.log(paddedPenceNumberString.charAt(0));
+
 
 const pence = paddedPenceNumberString
   .substring(paddedPenceNumberString.length - 2)
@@ -25,3 +27,34 @@ console.log(`£${pounds}.${pence}`);
 
 // To begin, we can start with
 // 1. const penceString = "399p": initialises a string variable with the value "399p"
+/* 
+ * 2. const penceStringWithoutTrailingP = penceString.substring( penceString.length - 1);
+  * Assign the penceStringWithoutTrailingP variable to  string penceString trailing last char of it.
+  * length of penceString - 1 because index begins to 0
+  * String method substring() parameter does not accept negative index (unlike slice)
+  * String method substring() returns charAt(3) to the end.
+  * penceString is not muted (remains the same).
+  * 
+ * 3. const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+  * penceStringWithoutTrailingP.padStart(3, "0") = add (number - string.length) "0"
+  * Here penceStringWithoutTrailingP.length = 3 so 3 - 3 = nothing to add.
+  * useful to add 0 if the price < 1 pound (Impossible nowadays).
+
+ * 4. const pounds = paddedPenceNumberString.substring( 0, paddedPenceNumberString.length - 2);
+  * String method substring() returns charAt(0) to charAt(1)(3- 1) non inclusif,
+  * Equivalent to substring( 0, 1);
+  * Equivalent to paddedPenceNumberString.charAt(0);
+
+ * 5. const pence = paddedPenceNumberString
+  .substring(paddedPenceNumberString.length - 2)
+  .padEnd(2, "0");
+  * String method substring() returns the 2 last char of the string.
+  * Here the pences.
+  * padEnd(2, "0") same system than above but add "0" at the end if the string.length < 2
+  * E.g. "9" => "90".
+
+ * 6. console.log(`£${pounds}.${pence}`);
+  * Display in the console currency + pound's value + separator + pence's value
+  * thanks to the template literals ``.
+
+*/

Sprint-1/4-stretch-explore/objects.md

@@ -14,3 +14,7 @@ Answer the following questions:
 
 What does `console` store?
 What does the syntax `console.log` or `console.assert` mean? In particular, what does the `.` mean?
+- console.log(["message"], value.toString())
+- console.assert(assertion, "message", [optionalParams]);
+- - assertion returns a boolean (false / true). If false the message will be displayed in the console.
+- - E.g. console.assert(5 < 2, "You are really dumb into mathematics");

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

@@ -1,13 +1,16 @@
 // Predict and explain first...
-//  =============> write your prediction here
+//  Guess init a variable with the same name than the argument is not a good idea.
 
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
 
-function capitalise(str) {
+/* function capitalise(str) {
   let str = `${str[0].toUpperCase()}${str.slice(1)}`;
   return str;
-}
+} */
 
-// =============> write your explanation here
-// =============> write your new code here
+// SyntaxError: Identifier 'str' has already been declared
+ function capitalise(str) {
+  return `${str[0].toUpperCase()}${str.slice(1)}`;
+} 
+console.log(capitalise("hello world"));

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

@@ -1,20 +1,27 @@
 // Predict and explain first...
 
 // Why will an error occur when this program runs?
-// =============> write your prediction here
+// Variable 'decimalNumber' is already declared. And this declaration is no needed.
+// console.log(decimalNumber); will throw an error. const is block scoped.
 
 // Try playing computer with the example to work out what is going on
 
-function convertToPercentage(decimalNumber) {
+/* function convertToPercentage(decimalNumber) {
   const decimalNumber = 0.5;
   const percentage = `${decimalNumber * 100}%`;
 
   return percentage;
 }
 
-console.log(decimalNumber);
+console.log(decimalNumber); */
 
-// =============> write your explanation here
+// SyntaxError: Identifier 'decimalNumber' has already been declared
 
 // Finally, correct the code to fix the problem
-// =============> write your new code here
+function convertToPercentage(decimalNumber) {
+  const percentage = `${decimalNumber * 100}%`;
+  return percentage;
+}
+
+console.log(convertToPercentage(0.5));
+

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

@@ -3,18 +3,23 @@
 
 // this function should square any number but instead we're going to get an error
 
-// =============> write your prediction of the error here
+// '3' is a number not an argument.
 
-function square(3) {
+/* function square(3) {
     return num * num;
-}
+} */
 
-// =============> write the error message here
+// SyntaxError: Unexpected number
 
-// =============> explain this error message here
+// '3' is a number not an argument. 
+// An argument is a variable and must not begin with a number.
+// the var 'num' is coming from nowhere.
 
 // Finally, correct the code to fix the problem
 
-// =============> write your new code here
+function square(num) {
+    return num * num;
+}
 
+console.log(square(3));