Could someone please help me to change this JavaScript code snippet to a function?

2. <script>
3. var headertext = [],
4. headers = document.querySelectorAll("#responsiveTable th"),
5. tablerows = document.querySelectorAll("#responsiveTable th"),
6. tablebody = document.querySelector("#responsiveTable tbody");
7. 
   
8. for(var i = 0; i < headers.length; i++) {
9.   var current = headers[i];
10.   headertext.push(current.textContent.replace(/\r?\n|\r/,""));
11. }
12. for (var i = 0, row; row = tablebody.rows[i]; i++) {
13.   for (var j = 0, col; col = row.cells[j]; j++) {
14.     col.setAttribute("data-th", headertext[j]);
15.   }
16. }
17. </script>