:containsNoCase

Example

// Search Filter - filter based on textbox input all list elements
$('#txtSearch').keyup(function() {
    var search = $(this).val();
    if (!search)
        $(".list-item").show();  // show all items
    else
        // show only those that have text matching search text
        $(".list-item").hide().filter(":containsNoCase('" + search + "')").show();
});