What is the javascript equivalent of the PHP auto-assigning array feature?

Question

I am trying to automatically update a javascript array, without specifying a number or string for the key. The value should just take up the next numeric key in the array.

In php you can do this:

<? 
myarray = array();
myarray[] = '1';
myarray[] = '2';
myarray[] = '3';

//this is equivalent to myarray[1] = '1', myarray[2] = '2', myarray[3] = '3'; 


?>

how can I do this in javascript?

this throws an error

$(function(){

var optionset = [];        

optionset[] = 'a';
optionset[] = 'b';

}); 

Answer 1

optionset.push('a', 'b');

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/push

Mutates an array by appending the given elements and returning the new length of the array.

Answer 2

 optionset.push('a');
 optionset.push('b');

See push() on W3Schools for more details.