var y;     // variable declaration

var x = 3; // variable declaration and assignment

​

// test if something is an expression by putting it in a console.log

// there will be no errors if it is an expression

console.log(x);

​

​

// remember that these are expressions:

/*

raw data

variables

function calls

calculations

function declarations (less important)

*/

// remember that these are statements

/*

function calls

function declarations 

variable declarations

variable assignments

if statements

loops

*/