Dynamically Change Row Colour On Dynamically Generated Table Rows

At this point I have been able to add the row. But what I want to do and am having trouble with is alternating the row colour to the dynamically added row element.

Sample of code I am using:

Code:
var tbody = document.getElementById('tableItems');

var row = document.createElement("tr");

var remainder = tbody.rows.length % 2;
if(remainder) {
row.setAttribute("class", "rowLightGreen");
}

var td1 = document.createElement("td");
td1.appendChild(document.createTextNode(qty));
td1.setAttribute("class","qty");
row.appendChild(td1);
tbody.appendChild(row);
One thing that puzzles me, is that even after adding a row the table my table.rows.length still = 0.

Does anyone know how I can determine the appropriate amount of rows so that I can apply the appropriate class?

Or is there just something blatantly wrong in my approach?