javascript

how to write a comments in javascript:

inline comments:

(sample script) //this is an inline comment

multi-line comments:

/* this is a multi-line comment*/

javascript data types:

undefined = something that hasn't been defined

null = nothing
boolean = true or false
string = any sort of text
symbol = immutable primitive vaule that is unique
number = number
object =

How to use variables:

The three ways to declare variables:

1 let (for example: let myname = "mateocoltura")
2 const (for example: const pi = 3.14)
3 var (for example: var myname = "mateo", var myname= "8" )

Difference between var, const, and let:

var is able to be used troughout your whole program
let wil only will be used within the scope where you declare it
const is a variable that should/can never change

declaring a variable (declaring and assigning in one line) :

var b = 2;

assigning a variable (letting it be called a for example):

var a;

now i can give a a value without var before it because it has already been assigned:

a = 7;
b = a;

this can be used in the console:

if var a = 7 when i type: "console.log(a)" it will display 7 in the console

uninitalized variables:

var a;
var b;
var c;

initialzed variables:

var a = 5;
var b = 10;
var c = "i am a string" (must always be between quotation marks)

calculating with initialized variables:

if "var a = 5;" then "a = a + 1;" equals: "6"
if "var b = 10;" then "b = b + 5;" equals: "15"
if "var c = "I am a" then "c = c + "String";" equals: "I am a string!"

VARIABLE DECLARATIONS AND ASSIGNMENTS ARE CASE SENSITIVE, if you have multiple things to declare to a var you use studlyCapVar by starting the first word with a lowercase and the next words with Uppercase, for example:

johnLucasBob
ericaThomasJade
AppleBottomJeans

Adding numbers in javascript:

var sum = 10 + 10;

Subtracting numbers in javascript:

var difference = 20 - 10;

Multiplying numbers in javascript:

var product = 8 * 1;

Dividing numbers in javascript:

var quotient = 66 / 2;


for example: if "var sum = 10 + 10" then "console.log(sum)" will display the number 20 in the console

Incrementing numbers:

if "var myVar = 87;" then you can increment by doing: "myVar++;"

Decrementing numbers:

if "var Myvar = 87;" then you can decrement by doing: "Myvar--;"

Decimal numbers:

var myDecimal = 0.009

Multiplying decimal numbers:

var product = 2.0 * 2.5;

Dividing decimal numbers:

var quotient = 4.4 / 2.0;

Finding a remainder: (the remainder operator gives the remainder of a division of two numbers)

  var remainder = 11 % 3; (=2)

The remainder operator is often used to determine if a number is even or odd,
if you can divide a number by 2 and the remainder is 0 that means the number is even


Compound assignment with augmented addition:

var a = 3;

a = a + 12

shortcut:

a += 12

Compound assignment with augmented substraction:

var a = 11;

a = a - 6;

shortcut:

a -= 6;

Compound assignemt with augmented multiplication:

var a = 5;

a = a * 5;

shortcut:

a *= 5

compound assignemt with augmented division:

var a = 48;

a = a / 12

shortcut:

a /= 12

Declaring string variables:

var myFirstName = "Mateo";
var myLastName = "Coltura";

Escaping literal quotes in strings:

var myStr = "i am a "double quoted" string inside "double quotes"

what you should do when you want to use quotes inside a string:

var myStr = "I am a \"double quoted\" string inside \"double quotes\" "

Quoting strings with single quotes:

var myStr = "< a href=\"https://www.example.com\" target= \"_blank\">Link</a>

what you should do is use single quotation marks because you can also use them.

var myStr = '<a href="https://www.example.com" target="blank">link</a>