jquery统计输入文字的个数并对其进行判断

<script type="text/javascript"> 
$(function() { 

function albumName() { 
var text = $("#album_name").val(); 
var counter = text.length; 
$("#numtj var").text(counter); 
$(document).keyup(function() { 
var text = $("#album_name").val(); 
var counter = text.length; 
$("#name_word").text(counter); 
}); 
} 
}); 
</script>

<input type="text" maxlength="30" class="int_txt" name="album_name" id="album_name"> 
<span class="count_txt"><span id="name_word">0</span>/30</span>