Пример:
Выбрать все отмеченные элементы формы.
"jQuery"
function countChecked() {
var n = $("input:checked").length;
$("div").text(n + (n == 1 ? " is" : " are") + " checked!");
}
countChecked();
$(":checkbox").click(countChecked);
"HTML"
<form>
<input type="checkbox" name="newsletter" checked="checked" value="Hourly" />
<input type="checkbox" name="newsletter" value="Daily" />
<input type="checkbox" name="newsletter" value="Weekly" />
<input type="checkbox" name="newsletter" checked="checked" value="Monthly" />
<input type="checkbox" name="newsletter" value="Yearly" />
</form>
<div></div>
"CSS"
div { color:red; }
"Живой пример jQuery"
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<link href="http://slyweb.ru/css/jqueryiframe.css"
rel="stylesheet" type="text/css"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js"></script>
<script>
$(document).ready(function(){
function countChecked() {
var n = $("input:checked").length;
$("div").text(n + (n == 1 ? " is" : " are") + " checked!");
}
countChecked();
$(":checkbox").click(countChecked);
});
</script>
</head>
<body class="iframe">
<form>
<input type="checkbox" name="newsletter" checked="checked" value="Hourly" />
<input type="checkbox" name="newsletter" value="Daily" />
<input type="checkbox" name="newsletter" value="Weekly" />
<input type="checkbox" name="newsletter" checked="checked" value="Monthly" />
<input type="checkbox" name="newsletter" value="Yearly" />
</form>
<div></div>
</body>
</html>
<style>
div { color:red; }
</style>