Javascript Basic Cheat Sheet by oren01

Print to console

consol­e.l­og(...)

One line	// single line comment
Multi lines	/* A multi line comment */

number	3, 3.1, -3.1, 3e5, 3e-5
string	"­abc­", 'abc', "­", ''
boolean	true, false
undefined	No value
null	Value of nothing
NaN	Not a number

var x = 3.1415;	Declare a number
x.toFi­xed(2)	To string, fixed decimals
parseI­nt(­"­2")	Convert a string to int
parseF­loa­t("1.23­")	Convert a string to float

var s = "­Hel­lo"	Declare and assign a string
s.length	Length of string
s.char­At(0)	Access a character at index
s.inde­xOf­("el­")	Index of a substring
s.slice(2, 4)	Part of string (start, end)

+, -, *, /	Add, subtract, multiply, divide
%	Modulus (reminder)
=	Assignment
++, --	Increment, decrement
+=, -=, *=, /=, %=	Operation and assignment
?	a = (x > y)? b: c;

==, !=	Equal to, not equal
===, !==	with type
>, <, >=, <=	Greate­r/Less or equal
&&, ||, !	And, Or, Not

Declare a function	function myFunc(p1, p2) {     statements;  ­ ­ ­ return p1 + p2; }
Use a function	x = myFunc(1, 5);
Function variable	var f = functi­on(p1, p2) {     statements;     return p1 + p2; };
Use function varialbe	x = f(1, 5);

if	if (x > y) {     statements; }
if..else	if (x > y) {     statements; } else {  ­ ­ ­ ­sta­tem­ents; }
if..else if	if (x > y) {     statements; } else if (x > z) {     statements; } else {  ­ ­ ­ ­sta­tem­ents; }
switch..case	switch(x) {     case 1:         statements;         break;     case 2:         statements;         break;     default:         statements; }

while	var x = 0; while (x < y) {     statements;     ++x; }
for	for (var x = 0; x < y; ++x) {     statements; }
continue	Stop current iteration, continue with next one
break	Stop loop immedi­ately
for/in	var x = [ "­abc­", "­efg­", "­hij­" ]; for (i in x) {     statements; // i = 0,1,2... }
for/of	var x = [ "­abc­", "­efg­", "­hij­" ]; for (i of x) {     statements; // i = "abc","efg",.. }

var a = [8, "­hi", 6]	Declare and assign
var a = []	Declare empty array
a[0]	Extract the first element
a[0] = "­xx"	Set the first element
a.length	Length of array
a.push(17)	Add element to array
a.pop()	Remove the last element
a.splice(  s, r,  e1, e2..)	From index s, remove r elements, then add e1, e2...
a.forE­ach(f)	Run function f(e) for each element in array

Literal object	var x = {   name: "cool",   size: 10,   sayHi = function() {     console.log(this.name);   } }
Constr­uctor	function MyObj(nm) {   this.name = nm;   this.size = 10;   this.sayHi = function() {     console.log(this.name);   } }
Create new object	var x = new MyObj(­"­coo­l");
Use object	console.log(x.size); x.sayHi();