Delete all rows in an HTML table

How can I delete all rows of an HTML table except the <th>'s using Javascript, and without looping through all the rows in the table? I have a very huge table and I don't want to freeze the UI while I'm looping through the rows to delete them

this will remove all the rows:

$("#table_of_items tr").remove(); 

Keep the <th> row in a <thead> and the other rows in a <tbody> then replace the <tbody> with a new, empty one.

i.e.

var new_tbody = document.createElement('tbody');
populate_with_new_rows(new_tbody);
old_tbody.parentNode.replaceChild(new_tbody, old_tbody)

Very crude, but this also works:

var Table = document.getElementById("mytable");
Table.innerHTML = "";