Why i always fail to make check mark to checkbox via javascript?

Look to my code below :

HTML :

<input type="checkbox" name="xyz[1][]" id="sel_44" style="margin:2px;" value="12345" onclick="myClick(this)">

Javascript :

<script>
$('#sel_44').attr("checked", true);
</script>

I already try every method (method that suggest by acceptance answer) in this URL : Check/Uncheck checkbox with javascript?

My Problem and Question :

I can sure $('#sel_loc_cb_44') is not null and not undefined. But i can make checkmark via javascript or jquery. How to fix my code and what's the source of problem?