getting value first offset name after click?

How can get value 2011 in input:na开发者_开发问答me with jquery?

<input type="text" name="hi[2011][]">

Example:

<button>Click me</button>
<input type="text" name="hi[2011][]">


$('button').click(function() {
    var f_offset = $('input').prop('name');
    alert(f_offset);
}

---

Using match:

$('button').click(function() {
    var f_offset = $('input').prop('name');
    alert(f_offset.match(/\d+/)[0]);
})

Example