jQuery忽略大小写过滤dom内容

<input id='search' type="text" placeholder="Search...">
<table id="downloads" class="table table-bordered table-hover" style="width:100%">
<script>
    // 重写jQuery语法
    jQuery.expr[':'].Contains = function (a, i, m) {
        return jQuery(a).text().toUpperCase()
            .indexOf(m[3].toUpperCase()) >= 0;
    };
</script>

$('#search').on('keyup click', function () {
    $('#downloads').DataTable().search($(this).val()
    ).draw();
});