How to use LIKE operator in Sheetrock

I'm trying to call the Javascript variable elem after LIKE in the SQL statement so that the input text is used there. However the way I'm doing it doesn't work with the Sheetrock library I'm using (http://chriszarate.github.io/sheetrock/).

<!DOCTYPE html>
<html>
<body>

Enter Tracking Code: <input type="text" id="textbox_id">
<input type="button" value="Submit">

<table id="switch-hitters" class="table table-condensed table-striped"></table>

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-sheetrock/1.0.1/dist/sheetrock.min.js"></script>


<script>

var mySpreadsheet = 'https://docs.google.com/spreadsheets/d/1_1elTo5zH1ew6KPYwoWtixX9hzFc8oxdRy5A0LWFkwg/edit#gid=0';
var elem =  document.getElementById('textbox_id').value;
$('#switch-hitters').sheetrock({
    url: mySpreadsheet,
    query: "select A,B,C,D,E where A LIKE %"+elem+"%"
});

</script>

</body>
</html>