Providing Add / Remove Functionality For Table Rows

I am trying to add functionality to a table that allows users to add and remove table rows, but I am stuck on the JS part of it. The JS I am working with allows users to add/remove table rows that are populated with text input fields, but I want it so where the rows are populated with these elements: 1) multiple select with populated options, 2) file upload box (input type="file"). How to modify the JS below to do this (I am new to JS).

Here is the JS I am working with:
Code:
function addRow(tableID) {
var table = document.getElementById(tableID);
var rowCount = table.rows.length;
var row = table.insertRow(rowCount);

var cell1 = row.insertCell(0);
var element1 = document.createElement("input");
element1.type = "checkbox";
cell1.appendChild(element1); .....