Myprojects/backend/s-26/discussion/index.js

console.log("Hello world!");


// An Array in programming is simply a list of data. Let's write the example earlier.

let studentNumberA = "2020-1923";
let studentNumberB = "2020-1924";
let studentNumberC = "2020-1925";
let studentNumberD = "2020-1926";
let studentNumberE = "2020-1927";

// Now, with an array, we can simply write the code above like this:
let studentNumbers = ["2020-1923", "2020-1924", "2020-1925", "2020-1926", "2020-1927"];

// [SECTION] Arrays
/*
	- Arrays are used to store multiple related values in a single variable.
	- They are declared using square brackets ([]) also known as "Array Literals"

	-Syntax:
		let/const arrayName = [elementA, elementB, elementC, ...]
*/

	// Common examples of arrays
	let grades = [98.5, 94.3, 89.2, 90.1];
	let computerBrands = ["Acer", "Asus", "Lenovo", "Neo", "Redfox", "Gateway", "Toshiba", "Fujitsu"];

	// Possible use of an array but is not recommended
	let mixedArr = [12, "Asus", null, undefined, {}];

	console.log(grades);
	console.log(computerBrands);
	console.log(mixedArr);

	// Alternative way to write an array
	let myTasks = [
		'drink html',
		'eat javascript',
		'inhale css',
		'bake react'
	]

	// Create an array with values from variables:
	let city1 = "Tokyo";
	let city2 = "Manila";
	let city3 = "Jakarta";

	let cities = [city1, city2, city3];

	console.log(myTasks);
	console.log(cities);

// [SECTION] length Property
	
	// The .length property allows us to get and set the total number of items in an array.

	console.log(myTasks.length);
	console.log(cities.length);

	let blankArr = [];
	console.log(blankArr.length);

	// .length property used on strings
	let fullName = "Jamie Noble";
	console.log(fullName.length);


	// .length property can also set the total number of items in an array.
	myTasks.length = myTasks.length - 1;
	console.log(myTasks.length);
	console.log(myTasks);

	// Another example using decrementation:
	cities.length--;
	console.log(cities);

	// We can't do the same on strings
	fullName.length = fullName.length - 1;
	console.log(fullName.length);


	// increase/lengthen the array
	let theBeatles = ["John", "Paul", "Ringo", "George"];
	theBeatles.length++;
	console.log(theBeatles);

// [SECTION] Reading from Arrays
/*
	- Accessing array elements is one of the more common tasks that we do with an array
	- This can be done through the use of array indexes
	
	- Syntax:
		arrayName[index]
*/

	console.log(grades[0]);
	console.log(computerBrands[3]);

	// Accessing an array element that does not exist will return "undefined"
	console.log(grades[20]);

	let lakersLegends = ["Kobe", "Shaq", "LeBron", "Magic", "Kareem"];

	// MINI ACTIVITY
	// Access the second item in the array:
	console.log(lakersLegends[1]);
	// Access the fourth item in the array:
	console.log(lakersLegends[3]);

	// Storing array item in a variable
	let currentLaker = lakersLegends[2];
	console.log(currentLaker);

	// Reassigning array values using item's index
	console.log("Array before reassignment:");
	console.log(lakersLegends);
	// reassign the 3rd item to "Paul Gasol":
	lakersLegends[2] = "Paul Gasol";
	console.log('Array after reassignment:');
	console.log(lakersLegends);


	// Accessing the last element of an array
	let bullsLegends = ["Jordan", "Pippen", "Rodman", "Rose", "Kukoc"]; // length = 5

	let lastElementIndex = bullsLegends.length - 2;
	console.log(bullsLegends[lastElementIndex]);

	[]


	// You can also add it directly:
	console.log(bullsLegends[bullsLegends.length - 1]);


	//Adding Items into the Array

	let newArr = [];
	console.log(newArr[0]);

	newArr[0] = "Cloud Strife";
	console.log(newArr);

	console.log(newArr[1]);
	newArr[1] = "Tifa Lockhart";
	console.log(newArr);

	// Adding an item at the end of the array
	newArr[newArr.length] = "Barrett Wallace";
	console.log(newArr);


	// Looping over an Array

	// You can use a for loop to iterate over all items in an array 

	for(let index = 0; index < newArr.length; index++){

		// You can use the loop counter (index) as index to be able to show each array items in a console log.
		console.log(newArr[index]);
	}

	// Given an array of numbers, you can also show if the following items in the array are divisible by 5 or not.
	let numArr = [5, 12, 30, 46, 40];

	for(let index = 0; index < numArr.length; index++){

		if(numArr[index] % 5 === 0){
			console.log(numArr[index] + " is divisible by 5");
		} else {
			console.log(numArr[index] + " is not divisible by 5");
		}
	}

// [SECTION] Multidimensional Arrays
	/*
		- Multidimensional arrays are useful for storing complex data structures
	*/

	let chessBoard = [
	    ['a1', 'b1', 'c1', 'd1', 'e1', 'f1', 'g1', 'h1'],
	    ['a2', 'b2', 'c2', 'd2', 'e2', 'f2', 'g2', 'h2'],
	    ['a3', 'b3', 'c3', 'd3', 'e3', 'f3', 'g3', 'h3'],
	    ['a4', 'b4', 'c4', 'd4', 'e4', 'f4', 'g4', 'h4'],
	    ['a5', 'b5', 'c5', 'd5', 'e5', 'f5', 'g5', 'h5'],
	    ['a6', 'b6', 'c6', 'd6', 'e6', 'f6', 'g6', 'h6'],
	    ['a7', 'b7', 'c7', 'd7', 'e7', 'f7', 'g7', 'h7'],
	    ['a8', 'b8', 'c8', 'd8', 'e8', 'f8', 'g8', 'h8']
	];

	console.log(chessBoard);

	// Accessing elements of a multidimensional array
	console.log(chessBoard[1][4]);

	console.log("Pawn moves to: " + chessBoard[1][5]);