JS选择checkbox

<script>
    window.onload = function () {
        //获取checkbox
        var ids1 = document.getElementsByName('VoteOption1');
        //获取值
        var choose1 = document.getElementById('ctl00_ContentPlaceHolder1_Facilities_864').value.split(',');

        for (var i = 0; i < ids1.length; i++) {
            if (contains(choose1, ids1[i].value))
            { ids1[i].checked = true; }
        }
    }

    //a:值
    //obj:checkbox
    function contains(a, obj) {
        var i = a.length;
        while (i--) {
            if (a[i] === obj) {
                return true;
            }
        }
        return false;
    }
</script>