What is the difference between these arrays?

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(); .

Answer 2

foo is an object, not an array. bar and another are arrays.

if you give foo['obj'] = new Date(); , obj will become a property of foo.

Answer 3

var foo = {}

This is an object, not an array.

var bar = new Array();

This is array but avoid new keyword with arrays .

var another = [];

This is correct way of initializing array.

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

There is no associative array in JS. You can instead do:

var foo = {};
var foo['obj'] = new Date();

Answer 4

bar and another are the same, but:

var foo = {}; 

foo is not an array rather an object

foo['obj'] = new Date(); //same as
foo.obj = new Date();

the advantage of f['obj'] is that you can use non-valid identifier characters ex:

   foo['test-me'] // is valid
   foo.test-me //not valid

Answer 5

var foo = {} is for object referal,
    foo = {myCar: "Saturn", getCar: CarTypes("Honda"), special: Sales}

while var bar = new Array(); is used to create new empty array.

But var another = []; can be used to assign any array empty values as well as creates empty array. I think for date you can use like foo[1] = new Date();