checkbox的全选和取消全选按钮的js

<span style="font-size:18px;">//全选、取消全选
function selectAll() {
var checked = $("#checkall").attr("checked");
$("input[name='checkbox_name']").each(function() {
if (checked) {
$(this).attr("checked", "checked");//全选
if (allarr.length > 0) {
for ( var i = 0; i < allarr.length; i++) {
if (allarr[i] != $(this).val()) {
allarr.push($(this).val());
break;
}
}
} else {
allarr.push($(this).val());
}
} else {
$(this).removeAttr("checked");//取消全选
for ( var i = 0; i < allarr.length; i++) {
if (allarr[i] == $(this).val()) {
allarr.splice(i, 1);
}
}
}
</span>});
}