Variables.txt

Variables

Var

In this lesson, we will cover how to use the var, let, and const keywords to create variables.

var myName = 'Arya';
console.log(myName);
// Output: Arya


Let’s consider the example above:

    var, short for variable, is a JavaScript keyword that creates, or declares, a new variable.
    myName is the variable’s name. Capitalizing in this way is a standard convention in JavaScript called camel casing. In camel casing you group words into one, the first word is lowercase, then every word that follows will have its first letter uppercased. (e.g. camelCaseEverything).
    = is the assignment operator. It assigns the value ('Arya') to the variable (myName).
    'Arya' is the value assigned (=) to the variable myName. You can also say that the myName variable is initialized with a value of 'Arya'.
    After the variable is declared, the string value 'Arya' is printed to the console by referencing the variable name: console.log(myName).

Variable let

let meal = 'Enchiladas';
console.log(meal); // Output: Enchiladas
meal = 'Burrito';
console.log(meal); // Output: Burrito
-------------------------------------------
let price;
console.log(price); // Output: undefined
price = 350;
console.log(price); // Output: 350
--------------------------------------------
let changeMe = true;

changeMe = false;

console.log(changeMe); //print false


variable const

const myName = 'Gilberto';
console.log(myName); // Output: Gilberto


variables 
Mathematical Assignment Operators

let w = 4;
w = w + 1;

console.log(w); // Output: 5
-----------------------------------------
let w = 4;
w += 1;

console.log(w); // Output: 4
---------------------------------------------
let x = 20;
x -= 5; // Can be written as x = x - 5
console.log(x); // Output: 15

let y = 50;
y *= 2; // Can be written as y = y * 2
console.log(y); // Output: 100

let z = 8;
z /= 2; // Can be written as z = z / 2
console.log(z); // Output: 4
----------------------------------------------
let levelUp = 10;

let powerLevel = 9001;
let multiplyMe = 32;
let quarterMe = 1152;

// Use the mathematical assignments in the space below:
levelUp += 5;
powerLevel -= 100;
multiplyMe *= 11
quarterMe /= 4

// These console.log() statements below will help you check the values of the variables.
// You do not need to edit these statements. 
console.log('The value of levelUp:', levelUp); 
console.log('The value of powerLevel:', powerLevel); 
console.log('The value of multiplyMe:', multiplyMe); 
console.log('The value of quarterMe:', quarterMe);


Variables
The Increment and Decrement Operator


let a = 10;
a++;
console.log(a); // Output: 11
-----------------------------------

let b = 20;
b--;
console.log(b); // Output: 19


String Concatenation with Variables
let myPet = 'armadillo';
console.log('I own a pet ' + myPet + '.'); 
// Output: 'I own a pet armadillo.'


String Interpolation

const myPet = 'armadillo';
console.log(`I own a pet ${myPet}.`);
// Output: I own a pet armadillo.
----------------------------------
const myName = 'Joao';
const myCity = 'Famalicao';
console.log(`My name is ${myName}. My favorite city is ${myCity}.`)

typeof operator

const unknown1 = 'foo';
console.log(typeof unknown1); // Output: string

const unknown2 = 10;
console.log(typeof unknown2); // Output: number

const unknown3 = true; 
console.log(typeof unknown3); // Output: boolean
-----------------------------------------------------------
let newVariable = 'Playing around with typeof.';
console.log(typeof newVariable);
newVariable = 1
console.log(typeof newVariable)