Question

var foo = {}
var bar = new Array();
var another = [];

Also, is it possible to add to foo like so:

foo['obj'] = new Date();

Answer 1

var foo = {};

foo is an object literal.

var bar = new Array();

bar is an array initialized via the Array constructor.

var another = [];

another is an array literal. Creating new arrays through literals is more efficient than doing so through the Array constructor: http://jsperf.com/new-array And it’s also much easier to type 😉 I’d recommend using array literals wherever possible.

Also, is it possible to add in foo like so: foo['obj'] = new Date();

Yes. That will add a property obj to foo with the value of new Date(). It’s equivalent to foo.obj = new Date();.