Regular expression [Any number]

I need to test for "[any number]" in a string in javascript. how would i match it?

Oh, "[" and "]" also need to be matched.

so string like "[1]" or "[12345]" is a match.

Non match: "[23432" or "1]"

So for example:

$('.form .section .parent').find('input.text').each(function(index){
      $(this).attr("name", $(this).attr("name").replace("[current]", "['"+index+"']"));
});

I need to replace input fields name: "items[0].firstname" to "items[1].firstname" thanks