Everything in JS is either an object or a primitive

Primitives

• Booleans: true , false

• Numbers: 42 , 3.14 , 0b11010 , 0x16 , NaN , Infinity

• Strings: 'Earth' , "Mars"

• Special values: undefined , null

Objects

The common way to declares is by using curly braces:

let myObj = { world: 'Earth' }

Attention: Objects are compared by reference. That being said, we have this:

let firstObj = {}
let secondObj = {}

// Check if they are equal
firstObj === secondObj
→ false

// Comparing an object with itself...
firstObj === firstObj
→ true

// Let's point the secondObj to firstObj
secondObj = firstObj

// Now they are equal
firstObj === secondObj
→ true

3; // = 3
1.5; // = 1.5

// Some basic arithmetic works as you'd expect.
1 + 1; // = 2
0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!)
8 - 1; // = 7
10 * 2; // = 20
35 / 5; // = 7

// Including uneven division.
5 / 2; // = 2.5

// Bitwise operations also work; when you perform a bitwise operation your float
// is converted to a signed int *up to* 32 bits.
1 << 2; // = 4

// Precedence is enforced with parentheses.
(1 + 3) * 2; // = 8

// There are special primitive values:
Infinity; // result of e.g. 1/0
-Infinity; // result of e.g. -1/0
NaN; // result of e.g. 0/0
undefined; // never use this yourself. This is the default value for "not assigned"
null; // use this instead. This is the programmer setting a var to "not assigned"

// There's also a boolean type.
true;
false;

// Strings are created with single quotes (') or double quotes (").
'abc';
"Hello, world";

// You can access characters in a string with `charAt`
"This is a string".charAt(0);  // = 'T'

// ...or use `substring` to get larger pieces.
"Hello world".substring(0, 5); // = "Hello"
"Hello world".slice(0, 5); // does the same thing
"Hello world".substr(0, 5); // yet again

// `length` is a property, so don't use ().
"Hello".length; // = 5

// Searching strings
"Mary had a little lamb".search("had"); // returns 5
"Mary had a little lamb".indexOf("zebra"); // returns -1

// String to a character array
"one two three four".split(" "); // ['one', 'two', 'three', 'four']

// String replace
"happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!"

// ES6 also introduces Symbol as a new primitive type
// But I'll add that on here once I actually figure out what it is