some code i don't understand well in jquery
<p>1,<code>$('input[id^="checkbox"]').click(function()</code></p>

<p>what's the <code>id^="checkbox"</code> meaning?</p>

<p>2,</p>

<pre><code>var checkall = $('#checkall');
var boxes = $('input[type="checkbox"]').not(checkall);

checkall.click(function () {
    boxes.attr('checked', this.checked);
});
boxes.change(function() {
    checkall[0].checked = this.checked &amp;&amp; boxes.filter(':checked').length === boxes.length;
});
</code></pre>

<p>a, <code>var boxes = $('input[type="checkbox"]').not(checkall);</code> </p>

<p>does this line mean "give all <code>type=checkbox</code> input to boxes expect the <code>id=checkall"</code></p>

<p>what's these lines meaning? <code>checkall[0].checked = this.checked &amp;&amp; boxes.filter(':checked').length === boxes.length</code>; and could i change this <code>boxes.attr('checked', this.checked)</code>; to <code>boxes.attr('checked', checked);</code> thank you</p>
