<script type="text/javascript"></script>

// or Include it in an external file (this is a comment)
/* This is also another way you can insert comments,
Multiline normally */

<script src="myscript.js"></script><code></code>

// PS: Remember to sub to our newsletter for the Giveaway!

var myVariable = 22; //this can be a string or number. var is globally defined

let myVariable = 22; //this can be a string or number. let can be reassigned

const myVariable = 22; //this can be a string or number. can't be reassigned

//string
let string = 'ASCII text';
//int
let integer = 123456789;
//float
let float = 123.456;
//boolean, can be true or false
let t = true;
let f = false;
//undefined
let undef;//defaults to undefined
let undef = undefined;//not common, use null
//null
let nul = null;
//array
let arr = ['Hello','my','name','is','Dr.Hippo',123,null];
//object
let person = {'name':'John Smith','age':27};
//function
let fun = function(){
    return 42;
}

+ — Addition
- — Subtraction
* — Multiplication
/ — Division
(...) — Grouping operator, operations within brackets are executed earlier than those outside
% — Modulus (remainder )
++ — Increment numbers
-- — Decrement numbers

== Equal to
=== Equal value and equal type
!= Not equal
!== Not equal value or not equal type
> Greater than
< Less than
>= Greater than or equal to
<= Less than or equal to
? Ternary operator

&& Logical and
|| Logical or
! Logical not

& AND statement
| OR statement
~ NOT
^ XOR
<< Left shift
>> Right shift
>>> Zero fill right shift

for (statement 1; statement 2; statement 3) {
  // Coooode
}

let i=0;
while (i < 10) {
    console.log(i);
    i++;
}

\' — Single quote
\" — Double quote
\\ — Backslash
\b — Backspace
\f — Form feed
\n — New line
\r — Carriage return
\t — Horizontal tabulator
\v — Vertical tabulator

concat(arr1,[...]) // Joins two or more arrays, and returns a copy of the joined arrays
copyWithin(target,[start],[end]) // Copies array elements within the array, to and from specified positions
entries() // Returns a key/value pair Array Iteration Object
every(function(currentval,[index],[arr]),[thisVal]) // Checks if every element in an array pass a test
fill(val,[start],[end]) // Fill the elements in an array with a static value
filter(function(currentval,[index],[arr]),[thisVal]) // Creates a new array with every element in an array that pass a test
find(function(currentval,[index],[arr]),[thisVal]) // Returns the value of the first element in an array that pass a test
findIndex(function(currentval,[index],[arr]),[thisVal]) // Returns the index of the first element in an array that pass a test
forEach(function(currentval,[index],[arr]),[thisVal]) // Calls a function for each array element
from(obj,[mapFunc],[thisVal]) // Creates an array from an object
includes(element,[start]) // Check if an array contains the specified element
indexOf(element,[start]) // Search the array for an element and returns its position
isArray(obj) // Checks whether an object is an array
join([seperator]) // Joins all elements of an array into a string
keys() // Returns a Array Iteration Object, containing the keys of the original array
lastIndexOf(element,[start]) // Search the array for an element, starting at the end, and returns its position
map(function(currentval,[index],[arr]),[thisVal]) // Creates a new array with the result of calling a function for each array element
pop() // Removes the last element of an array, and returns that element
push(item1,[...]) // Adds new elements to the end of an array, and returns the new length
reduce(function(total,currentval,[index],[arr]),[initVal]) // Reduce the values of an array to a single value (going left-to-right)
reduceRight(function(total,currentval,[index],[arr]),[initVal]) // Reduce the values of an array to a single value (going right-to-left)
reverse() // Reverses the order of the elements in an array
shift() // Removes the first element of an array, and returns that element
slice([start],[end]) // Selects a part of an array, and returns the new array
some(function(currentval,[index],[arr]),[thisVal]) // Checks if any of the elements in an array pass a test
sort([compareFunc]) // Sorts the elements of an array
splice(index,[quantity],[item1,...]) // Adds/Removes elements from an array
toString() // Converts an array to a string, and returns the result
unshift(item1,...) // Adds new elements to the beginning of an array, and returns the new length
valueOf() // Returns the primitive value of an array

function name(parameter1, parameter2, parameter3) {
  // code to be executed
}

function myFunction(p1, p2) {
  return p1 * p2;   // The function returns the product of p1 and p2
}

let x = myFunction(4, 3);   // Function is called, return value will end up in x

function myFunction(a, b) {
  return a * b;             // Function returns the product of a and b
}

// Convert Fahrenheit to Celsius:
function toCelsius(fahrenheit) {
  return (5/9) * (fahrenheit-32);
}
document.getElementById("demo").innerHTML = toCelsius(77);

E — Euler’s number
LN2 — The natural logarithm of 2
LN10 — Natural logarithm of 10
LOG2E — Base 2 logarithm of E
LOG10E — Base 10 logarithm of E
PI — The number PI
SQRT1_2 — Square root of 1/2
SQRT2 — The square root of 2

let d = new Date(); // We usually call it d or date

d.getDate() Returns the day of the month (from 1-31)
d.getDay()  Returns the day of the week (from 0-6)
d.getFullYear() Returns the year
d.getHours()    Returns the hour (from 0-23)
d.getMilliseconds() Returns the milliseconds (from 0-999)
d.getMinutes()  Returns the minutes (from 0-59)
d.getMonth()    Returns the month (from 0-11)
d.getSeconds()  Returns the seconds (from 0-59)