How to convert json encoded PHP array to an array in Javascript?

How to convert json encoded PHP array to an array in Javascript?

I am fetching the an json encoded array using AJAX from a php file, but in
javascript I need to use it as an array, how can I create an array in
Javascript
My AJAX call to PHP File:
$.ajax({
type:"POST",
url:"ajaxfetch.php",
success:function(result){
alert(result);
}
});
Output in PHP File :
Array
(
[0] => Array
(
[id] => 4
[deviceID] => xyz123
[latitude] => -33.80010128657071
[longitude] => 151.28747820854187
[altitude] => 34.78788787
[createdDate] => 2013-08-15 23:00:00
[delete] => 0
)
[1] => Array
(
[id] => 5
[deviceID] => jdkfhjskh344
[latitude] => -33.950198
[longitude] => 151.259302
[altitude] => 76.44455
[createdDate] => 2013-08-15 21:50:42
[delete] => 0
)
[2] => Array
(
[id] => 1
[deviceID] => abc223
[latitude] => -33.890542
[longitude] => 151.274856
[altitude] => 21.4454455
[createdDate] => 2013-08-15 20:00:00
[delete] => 0
)
)
I json encoded this array in PHP and ajax retrieved it and is outputted in
a string...
I m looking for the way I can create an array in Javascript with the
output I recieve in ajax response, so that I can come up with an array of
format:
var locations = [
['Bondi Beach', -33.890542, 151.274856, 4],
['Coogee Beach', -33.923036, 151.259052, 5],
['Cronulla Beach', -34.028249, 151.157507, 3],
['Manly Beach', -33.80010128657071, 151.28747820854187, 2],
['Maroubra Beach', -33.950198, 151.259302, 1]
];