js-intro.js

// We use variables to store some information. We can imagine them as some kind of boxes, 
// or storages, in which we place some data.
// To be able to re-access this data (to be able to reference them), we need to name them somehow. 
// So we can say that varibles (storages) are named or we can say labeled.



// 3 ways to declare variables in JS:
// var 
// let 
// const

let student; // var. declaration (saving a spot in memory)
console.log("Value is: ", student); // Value is:  undefined
student = "kevin"; // var. assignment (initialization) - giving it a value

let firstName = "sandra"; // declaration and initialization in the same time

// 🚨can't name it with number starting nor with JS reserved words:
// let 3students 🚫🚫🚫
// class, let, const, function, for, ... 🚫🚫🚫

// multiple var. declarations
let price, tax, total;

// use camelCase (but if you want to use snake_case is OK, just be consistent)
let totalPrice // camelCase
let total_amount // snake_case

let name; // lowercase
// let Name; 🚫🚫🚫


// this is single line comment
/* this is
multiple lines
comment */

// skip:
// numbers are immutable data types - can't change their value, you are actually creating a new variable with the same name 
// price = 7;
// price = 9;


// double quotes combined with single quotes (string)
let pizza = "margarita is 'the best' ";
console.log(pizza); // ==> margaritha is 'the best' 

// "const" is used when declaring a variable which value will be constant. 
// if we try to change its values we will get the error back

const name = 'Ana';
name = 'Marina';
 
// console:
// unknown: "name" is read-only

// Using "let" we can only declare a variable without assigning it a value. That is not the case with "const".
// Variable needs to be declared and initialized at the same time.

let name; // <== we can do this
 
const price; // <== error